Method and apparatus for performing communication in wireless communication system

ABSTRACT

Embodiments herein disclose a method for handling a RLF in a wireless communication system by a UE (100). The method includes receiving a measurement configuration including a second timer (150) from a SN (300). Further, the method includes configuring the UE with the second timer associated with a measurement report for a PSCell of the SN. Further, the method includes starting the second timer when the measurement report is triggered while a first timer (140) for the PSCell is running. Further, the method includes detecting an expiry of one of: the first timer and the second timer for the PSCell. Further, the method includes declaring a SCG RLF upon expiry of one of: the first timer and the second timer whichever is early. Further, the method includes initiating a SCG failure procedure towards a MN (300) upon declaring SCG RLF.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/KR2020/001751, filed Feb. 7, 2020, which claims priority to IndianPatent Application No. 201941005101, filed Feb. 8, 2019, and IndianPatent Application No. 201941005101, filed Feb. 3, 2020, the disclosuresof which are herein incorporated by reference in their entirety.

BACKGROUND 1. Field

The present disclosure relates to a wireless communication system, andmore specifically related to a method and user equipment (UE) fordetecting early radio link failure (RLF) and enabling faster recovery innew radio (NR) of a wireless communication system.

2. Description of Related Art

To meet the demand for wireless data traffic having increased sincedeployment of 4th generation (4G) communication systems, efforts havebeen made to develop an improved 5th generation (5G) or pre-5Gcommunication system. The 5G or pre-5G communication system is alsocalled a ‘beyond 4G network’ or a ‘post long term evolution (LTE)system’. The 5G communication system is considered to be implemented inhigher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplishhigher data rates. To decrease propagation loss of the radio waves andincrease the transmission distance, beamforming, massive multiple-inputmultiple-output (MIMO), full dimensional MIMO (FD-MIMO), array antenna,analog beamforming, and large scale antenna techniques are discussedwith respect to 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, hybrid frequency shift keying (FSK) andFeher's quadrature amplitude modulation (FQAM) and sliding windowsuperposition coding (SWSC) as an advanced coding modulation (ACM), andfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA) as an advanced access technologyhave been developed.

The Internet, which is a human centered connectivity network wherehumans generate and consume information, is now evolving to the Internetof things (IoT) where distributed entities, such as things, exchange andprocess information without human intervention. The Internet ofeverything (IoE), which is a combination of the IoT technology and thebig data processing technology through connection with a cloud server,has emerged. As technology elements, such as “sensing technology”,“wired/wireless communication and network infrastructure”, “serviceinterface technology”, and “security technology” have been demanded forIoT implementation, a sensor network, a machine-to-machine (M2M)communication, machine type communication (MTC), and so forth have beenrecently researched. Such an IoT environment may provide intelligentInternet technology services that create a new value to human life bycollecting and analyzing data generated among connected things. IoT maybe applied to a variety of fields including smart home, smart building,smart city, smart car or connected cars, smart grid, health care, smartappliances and advanced medical services through convergence andcombination between existing information technology (IT) and variousindustrial applications.

In line with this, various attempts have been made to apply 5Gcommunication systems to IoT networks. For example, technologies such asa sensor network, MTC, and M2M communication may be implemented bybeamforming, MIMO, and array antennas. Application of a cloud RAN as theabove-described big data processing technology may also be considered tobe as an example of convergence between the 5G technology and the IoTtechnology.

As described above, various services can be provided according to thedevelopment of a wireless communication system, and thus a method foreasily providing such services is required.

SUMMARY

The principal object of the embodiments herein is to provide a methodand UE to detect early RLF and enable faster recovery in a NR.

Embodiments herein disclose a method for handling a RLF in a wirelesscommunication system by a UE (100). The method includes receiving ameasurement configuration including a second timer (150) from a SN(300). Further, the method includes configuring the UE with the secondtimer associated with a measurement report for a PSCell of the SN.Further, the method includes starting the second timer when themeasurement report is triggered while a first timer (140) for the PSCellis running. Further, the method includes detecting an expiry of one of:the first timer and the second timer for the PSCell. Further, the methodincludes declaring a SCG RLF upon expiry of one of: the first timer andthe second timer whichever is early. Further, the method includesinitiating a SCG failure procedure towards a MN (300) upon declaring SCGRLF.

By the method of the present application, the service interruption timefor bearers handled by the SCG is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

This method is illustrated in the accompanying drawings, throughoutwhich like reference letters indicate corresponding parts in the variousfigures. The embodiments herein will be better understood from thefollowing description with reference to the drawings, in which:

FIG. 1A is a flow diagram illustrating step by step operations forPSCell RLF and SCG failure indication in MR-DC scenario where UE isconfigured with SRB only on MCG PCell, according to prior art;

FIG. 1B is a flow diagram illustrating step by step operations forPSCell RLF and SCG failure indication in MR-DC scenario where UE isconfigured with SRB1, SRB2 on MCG PCell and SRB3 on SCG PSCell,according to prior art;

FIG. 2A is a flow diagram illustrating step by step operations for earlySCG failure indication to MN in MR-DC scenario where SRBs are configuredonly on MCG where the MCG and SCG cells may belong to either EUTRAN orNR, according to an embodiment as disclosed herein;

FIG. 2B is a flow diagram illustrating a method for early SCG failureindication to MN in MR-DC scenario where SRB1, SRB2 are configured onMCG and SRB3 is configured on SCG where the MCG cells may belong toeither EUTRAN or NR and SCG cells belong to NR, according to anembodiment as disclosed herein;

FIG. 3A is a flow diagram illustrating step by step operations forattempting cell selection on LTE (or the next priority RAT) On T310expiry, according to an embodiment as disclosed herein;

FIG. 3B is a flow diagram illustrating step by step operations for themobility from NR or handover to LTE command from the network may not bereceived eventually leading to RLF due to T310 expiry, according to anembodiment as disclosed herein;

FIG. 4A is a flow diagram illustrating step by step operations forenables the UE to recover from service interruption by allowing the UEto perform connection establishment on the target cell faster than thecase where T312 is not applied, according to an embodiment as disclosedherein;

FIG. 4B is a flow diagram illustrating step by step operations for sendRRC setup request from Source eNB (LTE) to Target gNB (NR) on T312expire, according to an embodiment as disclosed herein;

FIG. 5A is a flow diagram illustrating step by step operations to stopT312 on satisfying leaving condition, according to an embodiment asdisclosed herein;

FIG. 5B is a flow diagram illustrating step by step operations torestart T312 on satisfying leaving condition, according to an embodimentas disclosed herein;

FIG. 6 is schematic view of the UE for handling the RLF in the wirelesscommunication system, according to embodiments as disclosed herein, and

FIG. 7 is a flow chart illustrating a method for handling the RLF in thewireless communication system, according to embodiments as disclosedherein.

FIG. 8 is a diagram illustrating a base station according to anotherembodiment of the present disclosure.

DETAILED DESCRIPTION

Accordingly, embodiments herein disclose a method for handling a RLF ina wireless communication system. The method includes receiving, by a UE,a measurement configuration including a second timer from a secondarynode (SN). Further, the method includes configuring the UE with thesecond timer associated with a measurement report for a PSCell of theSN. Further, the method includes starting, by the UE, the second timerwhen the corresponding measurement report is triggered while the firsttimer for the PSCell is running. Further, the method includes detecting,by the UE, an expiry of one of: the first timer and the second timer forthe PSCell. Further, the method includes declaring, by the UE, asecondary cell group (SCG) RLF upon expiry of the first timer or thesecond timer whichever is early. Further, the method includesinitiating, by the UE, a secondary cell group (SCG) failure proceduretowards a Master Node (MN) upon declaring SCG RLF.

In an embodiment, further, the method includes notifying, by the UE, aSCG failure message to the master node over a SRB1 via a Master CellGroup (MCG) link upon declaring the SCG RLF. The SCG failure messageincludes a cause value corresponding to failure type as one of: theexpiry of the first timer and the expiry of the second timer. Further,the method includes triggering, by the MN, a recovery of the SecondaryCell Group (SCG) radio link failure (RLF) based on the SCG failuremessage.

In an embodiment, further, the method includes setting, by the UE, afailure type as one of a first timer expiry and a second timer expiry.

In an embodiment, the UE sets the failure type as the first timerexpiry, if the expiry of the first timer is before the expiry of thesecond timer, else the UE sets the failure type as the second timerexpiry, if the expiry of the second timer is before the expiry of thefirst timer.

In an embodiment, further the method includes receiving, by the UE, ameasurement object and reporting configuration from the SN including asecond timer, wherein the second timer is associated with themeasurement report for the PSCell of the SN.

In an embodiment, determining, by the UE, the triggering of themeasurement report for the PSCell associated with the second timer whilea first timer for the PScell is running, and starting, by the UE, thesecond timer for the PScell.

In an embodiment, the measurement report for the PSCell is sent to thesecondary node (SN) over one of a Signaling Radio Bearer type 1 (SRB1)and a Signaling Radio Bearer type 3 (SRB3).

In an embodiment, declaring, by the UE, the SCG RLF based on thedetection of the expiry of the first timer or the second timer whicheveris early, and stopping the other timer which is not expired.

In an embodiment, initiating, by the UE, the SCG failure procedure basedon the declaration of the SCG RLF.

In an embodiment, the first timer is a T310 timer wherein the firsttimer is included during SCG addition and the second timer is T312 timerwherein the second timer is included in the measurement configurationfrom the SN.

In an embodiment, triggering, by the MN, the recovery of the SCG RLFbased on the SCG failure message includes receiving, by the UE, a RRCreconfiguration message from the master node over on SRB1.

Accordingly, embodiments herein disclose a UE for handling a RLF in awireless communication system. The UE includes a processor coupled witha memory. The processor receives a measurement configuration including asecond timer from a secondary node (SN). The method includes configuresthe UE with a second timer associated with a measurement report for aPSCell of the SN. Further, the processor starts the second timer whenthe corresponding measurement report is triggered while the first timerfor the PSCell is running. The processor detects an expiry of one of thefirst timer and the second timer for the PSCell. The processor declaresSCG RLF upon expiry of the first timer or the second timer whichever isearly. Further, the processor initiates a SCG failure procedure upon thedeclaration of SCG RLF.

These and other aspects of the embodiments herein will be betterappreciated and understood when considered in conjunction with thefollowing description and the accompanying drawings. It should beunderstood, however, that the following descriptions, while indicatingpreferred embodiments and numerous specific details thereof, are givenby way of illustration and not of limitation. Many changes andmodifications may be made within the scope of the embodiments hereinwithout departing from the spirit thereof, and the embodiments hereininclude all such modifications.

The embodiments herein and the various features and advantageous detailsthereof are explained more fully with reference to the non-limitingembodiments that are illustrated in the accompanying drawings anddetailed in the following description. Descriptions of well-knowncomponents and processing techniques are omitted so as to notunnecessarily obscure the embodiments herein. Also, the variousembodiments described herein are not necessarily mutually exclusive, assome embodiments can be combined with one or more other embodiments toform new embodiments. The term “or” as used herein, refers to anon-exclusive or, unless otherwise indicated. The examples used hereinare intended merely to facilitate an understanding of ways in which theembodiments herein can be practiced and to further enable those skilledin the art to practice the embodiments herein. Accordingly, the examplesshould not be construed as limiting the scope of the embodiments herein.

As is traditional in the field, embodiments may be described andillustrated in terms of blocks which carry out a described function orfunctions. These blocks, which may be referred to herein as units ormodules or the like, are physically implemented by analog or digitalcircuits such as logic gates, integrated circuits, microprocessors,microcontrollers, memory circuits, passive electronic components, activeelectronic components, optical components, hardwired circuits, or thelike, and may optionally be driven by firmware and software. Thecircuits may, for example, be embodied in one or more semiconductorchips, or on substrate supports such as printed circuit boards and thelike. The circuits constituting a block may be implemented by dedicatedhardware, or by a processor (e.g., one or more programmedmicroprocessors and associated circuitry), or by a combination ofdedicated hardware to perform some functions of the block and aprocessor to perform other functions of the block. Each block of theembodiments may be physically separated into two or more interacting anddiscrete blocks without departing from the scope of the invention.Likewise, the blocks of the embodiments may be physically combined intomore complex blocks without departing from the scope of the invention

The accompanying drawings are used to help easily understand varioustechnical features and it should be understood that the embodimentspresented herein are not limited by the accompanying drawings. As such,the present disclosure should be construed to extend to any alterations,equivalents and substitutes in addition to those which are particularlyset out in the accompanying drawings. Although the terms first, second,etc. may be used herein to describe various elements, these elementsshould not be limited by these terms. These terms are generally onlyused to distinguish one element from another.

In recent years, several advancements in wireless communicationtechnologies has been made in order to meet the growing broadband demandand the advent of new applications and services. The second generationof wireless communication system was developed to provide voice servicein a mobile environment. The third generation enhanced this further withthe support of data along with voice in the mobile environment. Inrecent years, the fourth generation wireless communication system hasbeen developed to provide high speed broadband data in mobilityenvironment. However, the advancements in fourth generationcommunication system (Long term evolution—LTE) suffers from lack ofresources and methods to meet the growing demand for broadband and newuse cases. Therefore, the fourth generation communication system isbeing further advanced and also the fifth generation (New Radio—NR) isbeing developed in order to meet this growing need for broadband withenhanced mobile broadband (eMBB) while also supporting new use caseslike ultra-reliable low latency commination (URLLC) and massive machinetype communication (mMTC).

The NR is an orthogonal frequency-division multiplexing (OFDM)-based airinterface designed to support the wide variation of 5G device-types,services, deployments and spectrum. The network monitors the devicebehavior and provides the necessary resources to a mobile device (e.g.,UE or the like) to perform any operation it requires (data—uplink ordownlink, calls etc.). The signal strength and quality experienced bythe mobile device varies according to the proximity of the mobile devicewith the gNB. The UE's near the cell are expected to have a bettersignal condition compared to the ones which are far from the gNB i.e.cell edge situation.

The network (i.e., RAN Node)—gNodeB in the NR (gNB)/eNB in the LTEalways maintains a context on the mobile device that are in active RRCconnection with it. At any point of time, the gNB can handover themobile device/the UE from its control (i.e., source cell) to another gNBor another cell (i.e., target cell), thus transferring the entirecontext of the particular device to the target cell. This decision istaken by the network optionally based on assistance received from theUE, with the help of measurement reports about neighbor cells. (i.e.,gNB configures the mobile device to measure the signal condition of theserving cell and neighboring cells that may belong to a different gNB).There is a specific measurement criteria, and a specific reportingcriteria to the network, both of which are configured by the serving gNBitself. Due to multiple reasons like weak signal condition, heavy loadon serving gNB etc., the serving gNB can handover the device to theneighbor cell or the target gNB and this could be done based onassistance received from the UE in form of measurement reports.

The UE is continuously monitoring the quality of its radio link toensure that the link is sufficiently in good conditions to successfullyreceive any transmission from a base station and to successfully maketransmissions to the base station. When the UE identifies that that linkquality has gone weak, the radio resource management (RRM) functionalityperforming radio link monitoring (RLM) at physical (PHY) layer sends outof synchronization (sync) indications to higher layers (i.e. RRC layer)thereby indicating the higher layer about the degradation in radio linkquality. Once the link degradation condition reaches the allowed limiti.e. a configured threshold condition, the UE enters a state of outagei.e. poor radio conditions where the UE experience Qout (out of syncindication from radio resource manager) due to high block error rate.The current specifications provision the use of a configured T310 timerin this state. The UE declares radio link failure (RLF) on the expiry ofthis timer T310 and initiates cell selection procedure to attemptrecovery. This timer value is kept long enough to give the UE sufficientopportunity to recover from the outage state and get back to good radiolink quality with the in sync indications from the PHY layer. On theother hand, the T310 timer is configured short enough to triggerrecovery on another cell and not impact the user service significantlyi.e. minimize service interruption time.

Typically, this state of outage or the bad radio link state where Qoutis satisfied, occurs when the UE is moving towards a cell edge of theserving cell. Therefore, it is very likely that there is a neighbor cellto whose coverage the UE is entering into. As a result, it is ideal thatthe network configures handover initiating measurement report such thatthere is sufficient time for the network to process the measurementreport, prepare the target cell for handover and to provide handovercommand before the radio link of the serving cell becomes too weak todecode the handover command from the network correctly. However, evenafter good network planning and network optimization there are somepractical cases where the direction, speed of each UE are different andthe cell coverage are not optimal in which case it may become toocomplex to come up with a configuration that is ideal to all the UEs inthe cell. The reporting configuration for the configured measurement isset such that there is no increased amount of signaling due tomeasurement reports. The network configure measurement reporting suchthat an action has to be taken based on the report from the UE. In mostcases, this results in handover and hence the network configures suchmeasurements to be reported only in cases where a handover is requiredby the UE. This sometimes leads to increased probability of the UEentering the state of experiencing Qout before the measurement report istriggered (due to unpredictability of the wireless channel and otherfactors such as UE mobility and speed).

The 3GPP study on HetNet Mobility Enhancements for the LTE concludedthat handover performance in HetNet deployments is worse than that inhomogeneous macro deployments. In a dense HetNet environment, increasednumber of handovers and the RLF could result in larger serviceinterruption time for the UE due to several factors including RLFrecovery interruption and Qout during the T310. Having a short value ofT310 being configured for the UE could result in cases where the UEdeclares the RLF prior to the measurement report being sent to thenetwork. This type of configuration eludes the UE from having theopportunity to request for handover or to recover from Qout. Therefore,the value of T310 is generally kept larger. It could also happen thatthe UE has satisfied the reporting criteria for a configured neighborfrequency and sent measurement report to the network soon after T310 isstarted at the UE. There is good possibility network will prepare targetcell of handover and send the handover command to the UE but the UEbeing in out of sync may not be able to receive the handover command.Eventually, the UE would declare the RLF after the expiry of T310.However, the triggering of measurement report by the UE is an indicationof neighbor cell with good radio conditions being available in thevicinity. Therefore, a mechanism for fast handover failurerecovery/early radio link failure detection was introduced with theconfiguration of T312 timer where the UE declares radio link failurebefore T310 timer expiry i.e. upon expiry of T312 timer. This earlydecision is made so that the UE is provided with sufficient opportunityto return to in sync state and the network is provided enoughopportunity to prepare handover with the target cell. The T312 timer wasintroduced and configured by the network for controlling this behaviorwhich is expected to minimize the service interruption time. When theRLF timer T310 is running and a measurement report is triggered by theUE for a combination of measurement object and reporting configurationrequiring the UE to use T312 timer based behavior, the UE starts thetimer T312. When T312 expires, the UE declares early RLF procedure andattempts for recovery of radio link. However, such early recovery isfeasible in the master cell group (MCG) but not in the secondary cellgroup (SCG) in the dual connectivity configuration. The RLF on the SCGis also referred to as the SCG failure and both terminologies areinter-changeably used here after in the disclosure. With the flexibilityin configuration of the Dedicated Radio Bearers (DRBs) in dualconnectivity architectures supported in the NR, the lower layer i.e. RLCleg can be flexibly configured in either MCG or SCG or both and can beassociated with a packet data convergence protocol (PDCP) entityterminated either at the master node or secondary node. Therefore, ifSCG failure is encountered on the PSCell in the SCG, it makes sense torecover early to minimize the service interruption time for bearershandled by the SCG.

Thus, it is desired to address the above mentioned disadvantages orother shortcomings or at least provide a useful alternative.

Accordingly embodiments herein disclose a method for handling a RLF in awireless communication system. The method includes receiving, by a UE, ameasurement configuration including a second timer from a secondary node(SN). Further, the method includes configuring the UE with the secondtimer associated with a measurement report for a PSCell of the SN.Further, the method includes starting, by the UE, the second timer whenthe corresponding measurement report is triggered while the first timerfor the PSCell is running. Further, the method includes detecting, bythe UE, an expiry of one of: the first timer and the second timer forthe PSCell. Further, the method includes declaring, by the UE, asecondary cell group (SCG) RLF upon expiry of the first timer or thesecond timer whichever is early. Further, the method includesinitiating, by the UE, a secondary cell group (SCG) failure proceduretowards a Master Node (MN) upon declaring SCG RLF.

The proposed method can be used to detect early RLF and enable fasterrecovery in NR. The method can be used to the T312 in RRCR configurationusing RLF-Timers and constants in spCellConfig. The method can be usedto indicate SCG failure cause due to T312 expiry.

The proposed method introduces T312 based mechanism on the PSCell forfast declaration of the SCG failure. This can facilitate less serviceinterruption time for the bearers configured over the SCG by expeditingthe SCG recovery based on shorter T312 timer.

Based on the proposed methods, when T312 expires for PSCell (i.e.secondary node with NR PSCell), the UE does not perform RRCre-establishment procedure but sends the SCG Failure message to thenetwork. The SCG failure message includes the cause value correspondingto T312 expiry. For PSCell RLF, the RRC Connection is already good onthe PCell (i.e. MN) but the data on the PSCell (i.e. SN) is lost. The UEattempts to restore the data on the SCG by autonomously sending thecause for the failure without the need for the NW to inquire. The SCGFailure message is sent to the Master Node (i.e. MN) on SRB1 via MCGlink, regardless of the SCG measurement are configured via SRB1 or SRB3.

The various embodiments of the proposed method is adopted in the 3GPP TS38.331.

Referring now to the drawings, and more particularly to FIGS. 2A through7, there are shown preferred embodiments.

FIG. 1A is a sequential flow diagram illustrating a method for PSCellRLF and SCG failure indication in a MR-DC scenario, where the UE (100)is configured with a SRB only on a MCG PCell, according to prior art.

The UE (100) can be configured with more than one serving cells. Thiscan either be in a carrier aggregation (CA) type of configuration whereall the serving cells belong to a same cell group (CG) served by a samegNB or in a dual connectivity configuration where the serving cellscould be from two different cells groups (CGs i.e. MCG and SCG) servedby two different gNBs. Radio link monitoring (RLM) is performed only onprimary cell (PCell) in the carrier aggregation (CA) case and on bothprimary cell and the primary secondary cell (PSCell) in dualconnectivity (DC) case. The PCell and PSCell are special cells andgenerally referred as Special cell i.e. SpCell.

In an embodiment, method can be used to detect the RLF or perform a SCGfailure recovery on the PSCell (use of T312 on the PScell/the SCG). Whenthe UE (100) is configured with a LTE dual connectivity i.e. (LTE-DC),all the measurement configuration and measurement reports are exchangedbetween the UE (100) and the eNB over signaling radio bearer 1 (SRB1).The master node (MN) is aware of the secondary node (SN) configurationand can comprehend them. The MN appends the configuration received fromthe SN and sends to the UE (100) in the RRC reconfiguration message. Anymeasurement report sent by the UE (100) will terminate at the MN eNB.

However, with the introduction and development of NR technology, the waythe SN configuration handled has changed. The NR supports multiple dualconnectivity based deployments types which includes EUTRA-NR DualConnectivity (EN-DC) where the MN is LTE eNB connected EPC and SN is NRgNB, NG-RAN E-UTRA-NR Dual Connectivity (NGEN-DC) where the MN is LTEng-eNB connected to the 5GC and SN is NR gNB, NR-E-UTRA DualConnectivity (NE-DC) where the MN is NR gNB connected to 5GC and SN isLTE ng-eNB and NR-NR Dual Connectivity (NR-DC) where MN is NR gNBconnected to 5GC and SN is NR gNB. These are collectively referred to asMulti-Radio Dual Connectivity (MR-DC). In the MR-DC, when SignalingRadio Bearers (SRB) are present only on the MN, the SN configurationsare transparent to the MN and the MN cannot comprehend theseconfigurations. The MN encapsulates the received SN configuration andsends in the reconfiguration message to the UE (100). When the SRB3hosted in the SN is configured to the UE (100) i.e. UE (100) isconfigured with both MN and SN hosted independent SRBs, the SNconfiguration is not sent to the MN and the SN directly sends RRCreconfiguration message to the UE (100) on the SRB3. Therefore, the MNand the SN can send independent reconfiguration message to the UE (100).

On both PCell and PSCell, the UE (100) monitors RLM. When Qout conditionis satisfied, the T310 is started for the cell and the RLF is declaredonce T310 expires. Timer based early detection is possible based on whenthe measurement report is triggered for the measurement object-reportingconfiguration combination that is required to use T312. In LTE T312based behavior is applied only to the primary cell (PCell) even in caseswhere the UE (100) is configured with dual connectivity operation i.e.LTE DC configuration. In MR-DC, PSCell RLF detection is based on T310itself as illustrated in the FIG. 1A and FIG. 1B. The FIG. 1Aillustrates the case where PSCell RLF and SCG failure indication in theMR-DC scenario where the UE (100) is configured with the SRB only on theMCG PCell. The SCG cells served by the SN in the MR-DC may either belongto the EUTRA or the NR. FIG. 1B illustrates the case where the PSCellRLF and the SCG failure indication in the MR-DC scenario where the UE(100) is configured with SRB1, SRB2 on the MCG PCell and SRB3 on the SCGPSCell. The SCG cells in this case belongs to the NR.

In an example, at S102 a, the SN (300) sends a measurement configurationto a MN (200). At S104 a, the MN (200) sends the measurementconfiguration to the UE (100). At S106 a, the data from SN bearers isestablished between the UE (100) and the SN (300). At S108 a, the SN(300) sends a RRC reconfiguration to the MN 200. At S110 a, the MN (300)sends the RRC reconfiguration to the UE (100). At S112 a, the UE (100)detects the Qout for the PSCell. At S114 a, the UE (100) starts thetimer (i.e., T310) for the PScell. At S116 a, the UE (100) sends ameasurement report to a MN (200) over the Signaling Radio Bearer type 1(SRB1) message. S118 a, the timer T310 is expired and the UE (100)initiates a secondary cell group (SCG) failure procedure at S120 a. AtS112 a, the UE (100) shares the SCG failure information to the MN (200).At S124 a, the MN (200) initiates the SCG failure recovery actions.

FIG. 1B is a sequential flow diagram illustrating step by stepoperations for PSCell RLF and SCG failure indication in the MR-DCscenario, where the UE (100) is configured with SRB1, SRB2 on the MCGPCell and SRB3 on the SCG PSCell, according to prior art.

The function and operations of the FIG. 1B is describe above inconjunction with the FIG. 1A. In an example, at S102 b, the SN (300)sends the measurement configuration to the UE (100). At S104 b, the datafrom the SN bearers is established between the UE (100) and the SN(300). At S106 b, the SN (300) sends the RRC reconfiguration to the UE(100). At S108 b, the UE (100) detects the Qout for the PSCell. At S110b, the UE (100) starts the timer (i.e., T310) for the PScell. At S112 b,the UE (100) sends the measurement report to the SN (300) over the SRB3message. At S114 b, the timer is expired and the UE (100) initiates theSCG failure procedure at S116 b. At S118 b, the UE (100) shares the SCGfailure information to the MN (200). At 120 b, the MN (200) initiatesthe SCG failure recovery actions.

FIG. 2A is a sequential flow diagram illustrating step by stepoperations for early SCG failure indication to the MN in the MR-DCscenario where the SRBs are configured only on the MCG where the MCG andSCG cells may belong to either the EUTRAN or the NR, according to anembodiment as disclosed herein.

The mechanism of declaring RLF early is to provide the UE (100) withopportunity to perform fast recovery. The T312 is used only when themeasurement report is triggered for the measurement configurationrequiring the use of T312. Typically, this is configured only forhandover triggering configurations. Therefore, if the UE (100) hastriggered the measurement report, it means that the UE (100) is invicinity of the cell in better signal conditions, so that handover ofongoing services can be performed. When T312 based early RLF declarationis adopted for the PCell, the UE (100) performs RRC re-establishmentearlier (most likely on the target cell indicated in the measurementreport) than that in case where only T310 is used. With the RRCre-establishment the target node retrieves the UE context from the oldserving node and restores the control and data path for the UE (100)thereby reducing the interruption caused to the UE (100) due to RLF.

Similarly, the T312 can be configured for PSCell when the measurementreport is triggered for the measurement configuration requiring the useof T312. Typically this will be configured only for the PSCell changetriggering condition. Therefore, if the UE (100) configured with MR-DCoperation, if the measurement report is triggered for the PSCell change,it means that the UE (100) is in vicinity of the cell in better signalconditions so that the PSCell change can be performed to offload theDRBs handled by serving PSCell. When the T312 based early RLFdeclaration is adopted for PSCell, the SCG failure is indicated to theMN upon T312 expiry i.e., earlier than what would have been reported ifonly T310 is used. This fast reporting of SCG failure provides the MNnode earlier opportunity to restore the data path that was configuredover SN on which the UE (100) encountered PSCell RLF or SCG failure. TheMN can restore the DRBs faster by either reconfiguring all the SNterminated PDU sessions or data radio bearers to MN terminated PDUsession or data radio bearers, or by preparing another SN andreconfiguring these bearers to the new SN. Since the PDU session/dataradio bearer relocation or reconfiguration occurs at an earlier timethan that on expiry of T310, it helps to reduce the service interruptiontimer for the UE (100) thereby providing a better user experience. FIG.2A and FIG. 2B illustrate the PSCell RLM and SCG failure indication tothe MN based on T312 timer. FIG. 2A illustrates early SCG failureindication to the MN in MR-DC scenario where the SRBs are configuredonly on MCG where the MCG and SCG cells may belong to either EUTRAN orNR. FIG. 2B illustrates early SCG failure indication to the MN in theMR-DC scenario where SRB1, SRB2 are configured on the MCG and the SRB3is configured on the SCG, where the MCG cells may belong to eitherEUTRAN or NR and SCG cells belong to the NR.

In an example, at S202 a, the SN (300) sends the measurementconfiguration to the MN (200), where the measurement configurationincludes the T312 timer. At S204 a, the MN (200) sends the measurementconfiguration to the UE (100). At 206 a, the data from SN bearers isestablished between the UE (100) and the SN (300). At 208 a, the SN(300) sends the RRC reconfiguration to the MN 200. At 210 a, the MN(300) sends the RRC reconfiguration to the UE (100). At S212 a, the UE(100) detects the Qout for the PSCell. At 214 a, the UE (100) starts thetimer (i.e., T310) for the PScell. At S216 a, the UE (100) sends themeasurement report to the MN (200) over the SRB1 message. At 218 a, theUE (100) starts the second timer (i.e., T312) and the second timer isexpired. At S220 a, the UE (100) initiates the SCG failure procedure. AtS222 a, the UE (100) shares the SCG failure information to the MN (200).At S224 a, the MN (200) initiates the SCG failure recovery actions.

FIG. 2B is sequential flow diagram illustrating step by step operationsfor early SCG failure indication to the MN in the MR-DC scenario whereSRB1, SRB2 are configured on the MCG and SRB3 is configured on the SCG,where the MCG cells may belong to either EUTRAN or NR and SCG cellsbelong to NR, according to an embodiment as disclosed herein.

In SN RRC reconfiguration sent to the UE (100) (either on SRB1 via MN ordirectly via SRB3), the network configures T312 timer value to the UE(100). This may be configured in one of the ways as following:

1. As part of measurement configuration provided by the SN to the UE(100), or

2. In RLF-TimersAndConstants in spCellConfig via RRC reconfigurationcontainer.

In an embodiment, the method configures the T312 as part of themeasurement configuration. The T312 value is normally configured forintra-RAT measurement objects configured for assisting the network intriggering PCell change procedure. However, it needs to be introducedeven for the measurement objects that are required for the SCG change orthe PSCell change.

Different deployment scenarios may need different time for handoverpreparation. For instance, the handover preparation time on Xn interfacefor an intra-gNB PCell change may be different from an inter-gNB basedPCell change which can again be different based on admission controlprocedure related to traffic and load on the target cell. Therefore, itis not optimal to configure the same value of T312 for all these cases.In order to efficiently meet the desired goal of early RLF detection,different T312 values may be configured for different measurementobjects. The measurement objects and reporting configuration related tochange of SCG or PSCell change should also be allowed to be configuredwith the T312 timer.

The T312 value may be configured as part of measurement object asillustrated below. In this case, the measurement object for which T312is set will be related to the frequencies on which PSCell change can beexecuted to. These are the frequencies served by SN nodes deployed inthe network.

 MeasObjectNR ::= SEQUENCE { ssbFrcqucncy ARFCN-ValucNR OPTIONAL, --Cond SSBorAssociatcdSSB ssbSubcarrierSpacing SubcarrierSpacingOPTIONAL, -- Cond SSBorAssociatedSSB smtc1 SSB-MTC OPTIONAL, -- CondSSBorAssociatedSSB ... t312-r16 CHOICE { release NULL, setup ENUMERATED{ms0, ms50, ms100, ms200, ms300, ms400, ms500, ms1000} } OPTIONAL,  --Need N ... }

or

MeasObjectNR ::= SEQUENCE { ssbFrequency ARFCN-ValueNR OPTIONAL, -- CondSSBorAssociatedSSB ssbSubcarricrSpacing SubcarrierSpacing OPTIONAL, --Cond SSBorAssociatedSSB smtc1 SSB-MTC OPTIONAL, -- CondSSBorAssociatedSSB ... t312-Config-r16 SetupRelease { T312-Config )OPTIONAL NEED N ... } T312-Config SEQUENCE { release NULL, setupENUMERATED {ms0, ms50, ms100, ms200, ms300, ms400, ms500 ms1000} }

or

MeasObjectNR ::= SEQUENCE { ssbFrequency ARFCN-ValueNR OPTIONAL, -- CondSSBorAssociatedSSB ssbSubcarrierSpacing SubcarrierSpacing OPTIONAL, --Cond SSBorAssociatedSSB smtc1 SSB-MTC OPTIONAL, -- CondSSBorAssociatedSSB ... t312-r16 ENUMERATED {ms0, ms50, ms100, ms200,ms300, ms400, ms500, ms 1000} OPTIONAL, -- Need R ... } ... }

The application of T312 for the particular measurement report is basedon the indication of T312 requirement for the configured reportingconfiguration. The T312 usage may be configured as a common IE which canbe applied for any reporting configuration within the EventTriggerConfigas illustrated below:

EventTriggerConfig::= SEQUENCE { eventId  CHOICE {  eventA1 SEQUENCE {a1-Threshold  MeasTriggerQuantity, reportOnLeave BOOLEAN, hysteresisHysteresis, timeToTrigger  TimeToTrigger  },  eventA2 SEQUENCE {a2-Threshold  MeasTriggerQuantity, reportOnLeave BOOLEAN, hysteresisHysteresis, timeToTrigger  TimeToTrigger  },  eventA3 SEQUENCE {a3-Offset  MeasTriggerQuantityOffset, reportOnLeave BOOLEAN, hysteresisHysteresis, timeToTrigger  TimeToTrigger, useWhiteCellList  BOOLEAN  }, eventA4 SEQUENCE { a4-Threshold  MeasTriggerQuantity, reportOnLeaveBOOLEAN, hysteresis Hysteresis, timeToTrigger  TimeToTrigger,useWhiteCellList  BOOLEAN  },  eventA5 SEQUENCE { a5-Threshold1 MeasTriggerQuantity, a5-Threshold2  MeasTriggerQuantity, reportOnLeaveBOOLEAN, hysteresis Hysteresis, timeToTrigger  TimeToTrigger,useWhiteCellList  BOOLEAN  },  eventA6 SEQUENCE { a6-Offset MeasTriggerQuantityOffset, reportOnLeave BOOLEAN, hysteresisHysteresis, timeToTrigger  TimeToTrigger, useWhiteCellList  BOOLEAN  }, ... }, rsType  NR-RS-Type, reportInterval ReportInterval, reportAmountENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity}, reportQuantityCell MeasReportQuantity, maxReportCells INTEGER (1..maxCellReport),reportQuantityRS-Indexes  MeasReportQuantity  OPTIONAL, -- Need RmaxNrofRS-IndexesToReport  INTEGER (1..maxNrofIndexesToReport) OPTIONAL, -- Need R includeBeamMeasurements  BOOLEAN,reportAddNeighMeas ENUMERATED {setup}  OPTIONAL, -- Need R  useT312BOOLEAN  OPTIONAL, -- Need N ...  }

Alternatively, the T312 usage can be signaled as a measurement eventspecific configuration within the EventTriggerConfig as illustratedbelow. Application of the T312 may be configured for all eventsindependently. The use of T312 is not limited to the illustration belowalthough the main use cases where the network may configure T312 is onlyfor the cases present in the below illustration.

EventTriggerConfig::= SEQUENCE { eventId CHOICE { eventA1 SEQUENCE { a1-Threshold  MeasTriggerQuantity,  reportOnLeave BOOLEAN,  hysteresis Hysteresis,  timeToTrigger  TimeToTrigger }, eventA2 SEQUENCE { a2-Threshold   MeasTriggerQuantity,  reportOnLeave BOOLEAN,  hysteresis Hysteresis,  timeToTrigger  TimeToTrigger }, eventA3 SEQUENCE { a3-Offset  MeasTriggerQuantityOffset,  reportOnLeave BOOLEAN, hysteresis  Hysteresis,  timeToTrigger  TimeToTrigger, useWhiteCellList  BOOLEAN useT312 BOOLEAN OPTIONAL, -- Need N },eventA4 SEQUENCE {  a4-Threshold  MeasTriggerQuantity,  reportOnLeaveBOOLEAN,  hysteresis  Hysteresis,  timeToTrigger  TimeToTrigger, useWhiteCellList  BOOLEAN }, evcntA5 SEQUENCE { a5-Threshold1MeasTriggerQuantity, a5-Threshold2 MeasTriggerQuantity, reportOnLeave BOOLEAN, hysteresis Hysteresis, timeToTrigger  TimeToTrigger,useWhiteCellList BOOLEAN useT312 BOOLEAN OPTIONAL, -- Need N }, eventA6SEQUENCE { a6-Offset  MeasTriggerQuantityOffset, reportOnLeave  BOOLEAN,hysteresis Hysteresis, timeToTrigger  TimeToTrigger, useWhiteCellListBOOLEAN }, ...  },  rsType  NR-RS-Type,  reportInterval ReportInterval, reportAmount  ENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity}, reportQuantityCell  MeasReportQuantity,  maxReportCells  INTEGER(1..maxCellReport), reportQuantityRS-Indexes MeasReportQuantityOPTIONAL, -- Need R maxNrofRS-IndexesToReport  INTEGER(1..maxNrofIndexesToReport) OPTIONAL, -- Need R  includeBeamMeasurements BOOLEAN,  reportAddNeighMeas  ENUMERATED {setup} OPTIONAL, -- Need R ... }

In another embodiment, the method can be used to configure T312 inRRCReconfiguration using RLF-Timers and constants in spCellConfig. In analternative method, the T312 value can be signaled as a UE specifictimer value and not measurement object dependent. In such cases, it isproposed that T312 is configured by the SN as part of spCellConfig usedin SCG modification, SCG change and SCG handover scenarios. The methodof configuring T312 for PSCell (or SCG) is as illustrated below:

RLF-TimersAndConstants ::=  SEQUENCE { t310 ENUMERATED {ms0, ms50,ms100, ms200, ms500, ms1000, ms2000, ms4000, ms6000}, n310  ENUMERATED{n1, n2, n3, n4, n6, n8, n10, n20}, n311  ENUMERATED {n1, n2, n3, n4,n5, n6, n8, n10},  t312 ENUMERATED {ms0, ms50, ms100, ms200,ms300,ms400, ms500, ms1000} ..., [[ t311-v1530  ENUMERATED {ms1000, ms3000,ms5000, ms10000, ms15000, ms20000, ms30000} ]] }

In another embodiment, the method can be used to indicate SCG failurecause due to T312 expiry. Once RLF has occurred on the PSCell (i.e. SCGfailure), the UE (100) initiates actions related to the SCG failure. TheSCG failure information is sent to the MN informing the network aboutthe failure of SCG link thereby indicating to network that recoveryactions need to be performed. This failure information additionallycarries the trigger or cause for this failure as well. The link failuredue to expiry of the T310 is different from that caused due to T312expiry. The T310 expiry would mean that the UE channel conditions becameunsuitable and could not sustain on that cell with the required quality.This does not reflect to the network the presence of a neighbor cell forpotential PSCell change. The UE (100) sends the results for all cells ithas detected in order to aid the network on the recovery procedures.However, T312 expiry would inform the network that the SCG link failureis due to degradation in the serving PSCell quality but also apprisesthe network that a neighbor cell with better signal conditions isavailable in the vicinity. It is possible that the network may changethe reporting configuration for these available neighbor cells in thefuture so that measurement reports may be sent prior to start of T310timer (prior to serving cell channel degrading to this extent).Moreover, it also important to the network and operator to differentiatethe RLF due to T312 expiry and due to T310 expiry in the network so thatcorrective configurations can be made. The corrective actions for T310expiry and T312 expiry will be different from network perspective.Therefore, it is important that the network identifies these failuresdifferently and hence would require the UE (100) to indicate themdistinctly to the network. Therefore, on an event of SCG failure (PScellRLF), the UE (100) should be provisioned to indicate RLF cause valueindicating T312 expiry as illustrated below:

SCG Failure Due to T312 Expiry for EN-DC and NGEN-DC:

-   -   5.7.3.3 Failure type determination for (NG)EN-DC

The UE shall set the SCG failure type as follows:

1> if the UE initiates transmission of the SCGFailureInformationNRmessage due to T310 expiry:

-   -   2> set the failureType as t310-Expiry;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to T312 expiry:

-   -   2> set the failureType as t312-Expiry;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide reconfiguration with sync failure information for anSCG:

-   -   2> set the failureType as synchReconfigFailure-SCG;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide random access problem indication from SCG MAC:

-   -   2> set the failureType as randomAccessProblem;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide indication from SCG RLC that the maximum number ofretransmissions has been reached:

-   -   2> set the failureType as rlc-MaxNumRetx;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to SRB3 IP check failure:

-   -   2> set the failureType as srb3-IntegrityFailure;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to Reconfiguration failure of NR RRC reconfigurationmessage:

-   -   2> set the failureType as scg-reconfigFailure.

SCGFailureInformationNR-r15 ::= SEQUENCE { criticalExtensions CHOICE {cl CHOICE { scgFailureInformationNR-r15 SCGFailureInformationNR-r15-IEs, spare3 NULL, spare2 NULL, spare1 NULL }, criticalExtensionsFutureSEQUENCE { } } } SCGFailureInformationNR-r15-IEs ::= SEQUENCE {failureReportSCG-NR-r15 FailureReportSCG-NR-r15 OPTIONAL,nonCriticalExtension SEQUENCE { } OPTIONAL } FailureReportSCG-NR-r15 ::=SEQUENCE { failureType-r15 ENUMERATED { t310-Expiry,randomAccessProblem, rlc- MaxNumRetx, scg- ChangeFailure,scg-reconfigFailure, srb3- IntegrityFailure, t312-Expiry},measResultFreqListNR-r15 MeasResultFreqListFailNR-r15 OPTIONAL,mcasRcsultSCG-r15 OCTET STRING OPTIONAL, ... }

The SCG failure due to T312 expiry for NE-DC: The use of T314 is onlyfor illustration. It may either be T314/T315/T312 etc.,

5.6.13.x Transfer of SCG Failure Information for NE-DC

The UE shall:

*1051> if SCG failure is due to T313 expiry:

-   -   2> consider the failureType to be t313-Expiry;

1> else if SCG failure is due to T314 expiry:

-   -   2> consider the failureType to be t314-Expiry;

1> else if SCG failure is due to indication from SCG MAC that a randomaccess problem was detected:

-   -   2> consider the failureType to be randomAccessProblem;

1> else if SCG failure is due to indication from SCG RLC that themaximum number of retransmissions was reached:

-   -   2> consider the failureType to be rlc-MaxNumRetx;

1> else if SCG failure is due to SCG change failure:

-   -   2> consider the failureType to be scg-ChangeFailure;

1> else if SCG failure is due to exceeding maximum uplink transmissiontiming difference:

-   -   2> include failureType and set it to maxUL-TimingDiff;

1> set the contents of the MeasResultSCG-FailureMRDC as follows:

-   -   2> for each measObjectEUTRA for which a measId is configured and        for which measurement results are available;        -   3> include an entry in measResultsFreqListEUTRA;        -   3> if a serving cell is associated with the MeasObjectEUTRA:        -   4> set measResultServingCell to include the available            quantities of the concerned cell and in accordance with the            performance requirements in TS 36.133 [16];    -   3> set the measResultNeighCellList to include the best measured        cells, ordered such that the best cell is listed first, and        based on measurements collected up to the moment the UE detected        the failure, including for each cell the optional fields for        which measurement results are available;    -   1> initiate transfer for SCG failure information i.e. of        failureType and MeasResultSCG-FailureMRDC via NR MCG embedded in        an NR RRC SCGFailureInformationEUTRA message as specified in TS        38.331 [X, 5.7.x]

SCGFailureInformation ::= SEQUENCE { criticalExtensions CHOICE {scgFailureInformation SCGFailureInformation-IEs,criticalExtensionsFuture SEQUENCE { } } } SCGFailureInformation-IEs ::=SEQUENCE { failureReportSCG FailureReportSCG OPTIONAL,nonCriticalExtension SEQUENCE { } OPTIONAL } FailureReportSCG ::=SEQUENCE { failureType ENUMERATED { t310-Expiry, randomAccessProblem,rlc- MaxNumRetx, synchReconfigFailure-SCG, scg-reconfigFailure, srb3-IntegrityFailure, t312-Expiry}, mcasRcsultFreqListMeasResultFreqListFail OPTIONAL, measResultSCG-Failure OCTET STRINGOPTIONAL, ... }

SCG failure due to T312 expiry for NR-DC:

SCGFailureInformationEUTRA ::= SEQUENCE { criticalExtensions CHOICE {scgFailureInformationEUTRA SCGFailureInformationEUTRA-IEs,criticalExtensionsFuture SEQUENCE { } } } SCGFailureInformationEUTRA-IEs::= SEQUENCE { failureReportSCG-EUTRA FailureReportSCG-EUTRA OPTIONAL,nonCriticalExtension SEQUENCE { } OPTIONAL } FailureReportSCG-EUTRA ::=SEQUENCE { failureType ENUMERATED { t313-Expiry, randomAccessProblem,rlc-MaxNumRetx, scg-ChangeFailure, maxUL-TimingDiff, t312-Expiry},measResultFreqListMRDC MeasResultFreqListFailMRDC OPTIONAL,measResultSCG-FailureMRDC OCTET STRING OPTIONAL, ... }

5.7.3.3 a Failure type determination for NR-DC

The UE shall set the SCG failure type as follows:

1> if the UE initiates transmission of the SCGFailureInformationNRmessage due to T310 expiry:

-   -   2> set the failureType as t310-Expiry;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to T312 expiry:

*132 2> set the failureType as t312-Expiry;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide reconfiguration with sync failure information for anSCG:

-   -   2> set the failureType as synchReconfigFailure-SCG;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide random access problem indication from SCG MAC:

-   -   2> set the failureType as randomAccessProblem;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage to provide indication from SCG RLC that the maximum number ofretransmissions has been reached:

-   -   2> set the failureType as rlc-MaxNumRetx;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to SRB3 IP check failure:

-   -   2> set the failureType as srb3-IntegrityFailure;

1> else if the UE initiates transmission of the SCGFailureInformationNRmessage due to Reconfiguration failure of NR RRC reconfigurationmessage:

-   -   2> set the failureType as scg-reconfigFailure.

In an embodiment, the method can be used to handle the timer T312 in NRstandalone operation (3GPP TS 38.331). In NR standalone scenario, thenetwork can configure T312 in one of the following processes illustratedearlier:

1. As a measurement object specific configuration within the measurementconfiguration from the gNB, or

2. As a UE specific configuration within RRCReconfiguration usingRLF-Timers And Constants in spCellConfig

If the T312 is configured for the UE (100), and measurement report istriggered when T310 is running for a measurement object and reportingconfiguration that are configured with T312, timer T312 is started asillustrated below.

5.4 Measurement Report Triggering

5.5.4.1 General

If security has been activated successfully, the UE shall:

1> for each measId included in the measIdList within VarMeasConfig:

. . .

-   -   2> if the reportType is set to eventTriggered and if the entry        condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells for all measurements after layer 3 filtering taken during        timeToTrigger defined for this event within the VarMeasConfig,        while the VarMeasReportList does not include a measurement        reporting entry for this measId (a first cell triggers the        event):        -   3> include a measurement reporting entry within the            VarMeasReportList for this measId;        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;    -   2> else if the reportType is set to eventTriggered and if the        entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells not included in the cellsTriggeredList for all        measurements after layer 3 filtering taken during timeToTrigger        defined for this event within the VarMeasConfig (a subsequent        cell triggers the event):        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;

In an embodiment, the timer T312 is stopped when handover command orreconfiguration with sync message is received from the network, or whenthe UE (100) initiates re-establishment message or when the UE (100)recovers from lower layer problems as illustrated below:

5.3.5.5.2 Reconfiguration with Sync

The UE shall perform the following actions to execute a reconfigurationwith sync.

1> if the security is not activated, perform the actions upon going toRRC_IDLE as specified in 5.3.11 with the release cause ‘other’ uponwhich the procedure ends;

1> stop timer T310 for the corresponding SpCell, if running;

1> if reconfigurationWithSync is received for PCell

-   -   2> stop timer T312 for the Pcell, if running;

1> start timer T304 for the corresponding SpCell with the timer valueset to t304, as included in the reconfigurationWithSync;

. . .

-   -   or

5.3.5.5.2 Reconfiguration with sync

The UE shall perform the following actions to execute a reconfigurationwith sync.

1> if the security is not activated, perform the actions upon going toRRC_IDLE as specified in 5.3.11 with the release cause ‘other’ uponwhich the procedure ends;

1> stop timer T310 for the corresponding SpCell, if running;

1> stop timer T312 for the corresponding SpCell, if running;

1> start timer T304 for the corresponding SpCell with the timer valueset to t304, as included in the reconfigurationWithSync;

. . .

5.3.7 RRC connection re-establishment

5.3.7.2 Initiation

The UE initiates the procedure when one of the following conditions ismet:

1> upon detecting radio link failure of the MCG, in accordance with5.3.10; or

1> upon re-configuration with sync failure of the MCG, in accordancewith sub-clause 5.3.5.8.3; or

1> upon mobility from NR failure, in accordance with sub-clause 5.4.3.5;or

1> upon integrity check failure indication from lower layers concerningSRB1 or SRB2, except if the integrity check failure is detected on theRRCReestablishment message; or

1> upon an RRC connection reconfiguration failure, in accordance withsub-clause 5.3.5.8.2.

Upon initiation of the procedure, the UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

1> stop timer T304, if running;

. . .

5.3.10.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the SpCellfrom lower layers while T310 is running, the UE shall:

1> stop timer T310 for the corresponding SpCell.

1> stop tinier T312 for the PCell, if running, when N311 consecutive“in-sync” indications is received on PCell

-   -   or

5.3.10.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the SpCellfrom lower layers while T310 is running, the UE shall:

1> stop timer T310 for the corresponding SpCell;

1> stop timer T312 for the corresponding SpCell.

When T312 expires, the UE (100) declares radio link failure (RLF) andinitiates radio link failure recovery using re-establishment procedureas illustrated below:

5.3.10.3 Detection of radio link failure

The UE shall:

1> upon T310 expiry in PCell; or

1> upon T312 expiry in PCell, or

1> upon random access problem indication from MCG MAC while neitherT300, T301, T304, T311 nor T319 are running; or

1> upon indication from MCG RLC that the maximum number ofretransmissions has been reached:

-   -   2> if CA duplication is configured and activated; and for the        corresponding logical channel allowedServingCells only includes        SCell(s):        -   3> initiate the failure information procedure as specified            in 5.7.5 to report RLC failure.    -   2> else:        -   3> consider radio link failure to be detected for the MCG            i.e. RLF;        -   3> if AS security has not been activated:            -   4> perform the actions upon going to RRC_IDLE as                specified in 5.3.11, with release cause ‘other’;        -   3> else if AS security has been activated but SRB2 and at            least one DRB have not been setup:            -   4> perform the actions upon going to RRC_IDLE as                specified in 5.3.11, with release cause ‘RRC connection                failure’;        -   3> else:            -   4> initiate the connection re-establishment procedure as                specified in 5.3.7.

In an embodiment, the method can be used to handle the T312 in (NG)EN-DC operation. Handling of T312 on LTE PCell/MCG in (NG) EN-DCoperation (3GPP TS 36.331), In (NG) EN-DC configuration or when the UE(100) is configured to operate in (NG) EN-DC, configuration of T312 maybe provided based on the existing signaling mechanisms provisioned inthe LTE specifications (as part of measurement configuration). Theconfiguration and value of T312 is provided as part of measurementobject configuration and the application of T312 is provided as part ofreporting configuration. The LTE (3GPP TS 36.331) already supports T312based early RLF declaration or fast handover recovery mechanism onPCell. If T312 is configured for the UE (100) on the MCG, andmeasurement report is triggered when T310 is running for the measurementobject and reporting configuration that are configured with T312, timerT312 is started as illustrated below:

5.5.4 Measurement Report Triggering

5.5.4.1 General

If security has been activated successfully, the UE shall:

1> for each measId included in the measIdList within VarMeasConfig

. . .

-   -   2> if the triggerType is set to event, and if the corresponding        reportConfig does not include numberOfTriggeringCells, and if        the entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells for all measurements after layer 3 filtering taken during        timeToTrigger defined for this event within the VarMeasConfig,        while the VarMeasReportList does not include a measurement        reporting entry for this measId (a first cell triggers the        event):        -   3> include a measurement reporting entry within the            VarMeasReportList for this measId;        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;    -   2> if the triggerType is set to event, and if the corresponding        reportConfig does not include numberOfTriggeringCells, and if        the entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells not included in the cellsTriggeredList for all        measurements after layer 3 filtering taken during timeToTrigger        defined for this event within the VarMeasConfig (a subsequent        cell triggers the event):        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;    -   3> initiate the measurement reporting procedure, as specified in        5.5.5;

Timer T312 is stopped when handover command from the network, or when UE(100) initiates re-establishment message or when the UE (100) recoversfrom lower layer problems as illustrated below:

5.3.5.4 Reception of an RRCConnectionReconfiguration including themobilityControlInfo by the UE (handover)

If the RRCConnectionReconfiguration message includes themobilityControlInfo and the UE is able to comply with the configurationincluded in this message, the UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

. . .

5.3.7 RRC connection re-establishment

5.3.7.2 Initiation

The UE shall only initiate the procedure either when AS security hasbeen activated or for a NB-IoT UE supporting RRC connectionre-establishment for the Control Plane CIoT EPS optimisation. The UEinitiates the procedure when one of the following conditions is met:

1> upon detecting radio link failure, in accordance with 5.3.11; or

1> upon handover failure, in accordance with 5.3.5.6; or

1> upon mobility from E-UTRA failure, in accordance with 5.4.3.5; or

1> upon integrity check failure indication from lower layers concerningSRB1 or SRB2; or

1> upon an RRC connection reconfiguration failure, in accordance with5.3.5.5; or

1> upon an RRC connection reconfiguration failure, in accordance withTS38.331 [82, 5.3.5.5].

Upon initiation of the procedure, the UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

. . .

5.3.11.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the PCell fromlower layers while T310 is running, the UE shall:

1> stop timer T310;

1> stop timer T312, if running;

. . .

5.4.3.3 Reception of the MobilityFromEUTRACommand by the UE

The UE shall be able to receive a MobilityFromEUTRACommand message andperform a cell change order to GERAN, even if no prior UE measurementshave been performed on the target cell.

The UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

When T312 expires, UE declares radio link failure (RLF) and initiatesradio link failure recovery using re-establishment procedure asillustrated below:

5.3.11.3 Detection of radio link failure

The UE shall:

1> upon T310 expiry; or

1> upon T312 expiry; or

1> upon random access problem indication from MCG MAC while neitherT300, T301, T304 nor T311 is running; or

1> upon indication from MCG RLC, which is allowed to be send on PCell,that the maximum number of retransmissions has been reached for an SRBor DRB:

In an embodiment, the method can be used to handle the T312 on NRPScell/SCG in (NG) EN-DC operation (3GPP TS 38.331). The network (i.e.,SN) can configure T312 to the UE (100) in (NG)EN-DC mode of operation,in one of the following methods either over SRB1 via MCG (container inMCG reconfiguration message) or over SRB3 directly to the UE (100):

As a measurement object specific configuration within the measurementconfiguration from gNB, or

As a UE specific configuration within RRCReconfiguration usingRLF-Timers and Constants in spCellConfig.

If T312 is configured for the UE (100), and measurement report istriggered when T310 is running for the measurement object and reportingconfiguration that are configured with T312, timer T312 is started asillustrated below.

5.5.4 Measurement report triggering

5.5.4.1 General

If security has been activated successfully, the UE

1> for each measId included in the measIdList within VarMeasConfig:

. . .

-   -   2> if the reportType is set to eventTriggered and if the entry        condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells for all measurements after layer 3 filtering taken during        timeToTrigger defined for this event within the VarMeasConfig,        while the VarMeasReportList does not include a measurement        reporting entry for this measId (a first cell triggers the        event):        -   3> include a measurement reporting entry within the            VarMeasReportList for this measId;        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;    -   2> else if the reportType is set to eventTriggered and if the        entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells not included in the cellsTriggeredList for all        measurements after layer 3 filtering taken during timeToTrigger        defined for this event within the VarMeasConfig (a subsequent        cell triggers the event):        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;            -   3> initiate the measurement reporting procedure, as                specified in 5.5.5;

The timer T312 is stopped when handover command or reconfiguration withsync message is received from the network, or when the UE (100)initiates re-establishment message or when the UE (100) recovers fromlower layer problems as illustrated below:

5.3.5.5.2 Reconfiguration with sync

The UE shall perform the following actions to execute a reconfigurationwith sync.

1> if the security is not activated, perform the actions upon going toRRC_IDLE as specified in 5.3.11 with the release cause ‘other’ uponwhich the procedure ends;

1> stop timer T310 for the corresponding SpCell, if running;

1> if reconfigurationWithSync is received for PSCell

-   -   2> stop timer T312 for the PScell, if running;

1> start timer T304 for the corresponding SpCell with the timer valueset to t304, as included in the reconfigurationWithSync;

. . .

-   -   or

5.3.5.5.2 Reconfiguration with sync

The UE shall perform the following actions to execute a reconfigurationwith sync.

1> if the security is not activated, perform the actions upon going toRRC_IDLE as specified in 5.3.11 with the release cause ‘other’ uponwhich the procedure ends;

1> stop timer T310 for the corresponding SpCell, if running;

1> stop timer T312 for the corresponding SpCell, if running;

1> start timer T304 for the corresponding SpCell with the timer valueset to t304, as included in the reconfigurationWithSync;

. . .

5.3.7 RRC connection re-establishment

5.3.7.2 Initiation

The UE initiates the procedure when one of the following conditions ismet:

1> upon detecting radio link failure of the MCG, in accordance with5.3.10; or

1> upon re-configuration with sync failure of the MCG, in accordancewith sub-clause 5.3.5.8.3; or

1> upon mobility from NR failure, in accordance with sub-clause 5.4.3.5;or

1> upon integrity check failure indication from lower layers concerningSRB1 or SRB2, except if the integrity check failure is detected on theRRCReestablishment message; or

1> upon an RRC connection reconfiguration failure, in accordance withsub-clause 5.3.5.8.2.

Upon initiation of the procedure, the UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

1> stop timer T304, if running;

. . .

5.3.10.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the SpCellfrom lower layers while T310 is running, the UE shall:

1> stop tinier T310 for the corresponding SpCell;

1> stop tinier T312 for the PSCell, if running, when N311 consecutive“in-sync” indications is received on PSCell

-   -   or

5.3.10.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the SpCellfrom lower layers while T310 is running, the UE shall:

1> stop timer T310 for the corresponding SpCell;

1> stop timer T312 for the corresponding SpCell.

5.3.5.4 Secondary cell group release

The UE shall:

1> as a result of SCG release triggered by E-UTRA:

-   -   2> reset SCG MAC, if configured;    -   2> for each RLC bearer that is part of the SCG configuration:        -   3> perform RLC bearer release procedure as specified in            5.3.5.5.3;    -   2> release the SCG configuration;    -   2> stop timer T310 for the corresponding SpCell, if running;    -   2> stop timer T312 for the corresponding SpCell, if running;    -   2> stop timer T304 for the corresponding SpCell, if running.

When T312 expires, the UE (100) declares SCG radio link failure or SCGfailure and initiates recovery using SCG failure information procedureas illustrated below:

5.3.10.3 Detection of Radio Link Failure

The UE shall:

. . .

The UE shall:

1> upon T310 expiry in PSCell; or

1> upon T312 expiry in PSCell; or

1> upon random access problem indication from SCG MAC; or

1> upon indication from SCG RLC that the maximum number ofretransmissions has been reached:

-   -   2> if CA duplication is configured and activated; and for the        corresponding logical channel allowedServingCells only includes        SCell(s):        -   3> initiate the failure information procedure as specified            in 5.7.5 to report RLC failure.    -   2> else:        -   3> consider radio link failure to be detected for the SCG            i.e. SCG-RLF;        -   3> initiate the SCG failure information procedure as            specified in 5.7.3 to report SCG radio link failure.

In an embodiment, the method can be used to handle the T312 in the NE-DCoperations. The method can be used to handle T312 on NR MCG/PCell inNE-DC operations (3GPP TS 38.331). The handling of the T312 andoperations based on T312 states on the NR MCG or PCell in NE-DCoperation is similar to that of NR standalone operation as illustratedin earlier section. The same operations and procedure for measurementreport triggering, start, stop and expiry of T312 is applicable here.

Method of handling T312 on LTE SCG/PSCell in NE-DC operation (3GPP TS36.331), LTE (3GPP TS 36.331) already supports T312 based early RLFdeclaration or fast handover recovery mechanism on PCell. However, inNE-DC configuration or when a UE is configured to operate in NE-DC, LTEcell is configured as PSCell or SCG. The fast handover recovery or earlyRLF declaration on LTE as a PSCell may be handled either by use of T312or using T314 or T315. In LTE, there is already T312 defined inspecification 3GPP TS 36.306 and 36.331 for handling of early RLFdeclaration or fast handover recovery mechanism. However, this is afeature from old release and reusing the same for SCG recovery may leadto backward compatibility issues. Therefore, a new timer say T314 orT315 has to be introduced in LTE to indicate the support of early SCGRLF declaration and fast SCG handover recovery. Otherwise, T312 may becommonly used to control early RLF declaration on both MCG and SCG. Insuch cases, a new UE capability for indicating support of T312 on SCGneed to be sent to the network to make network aware that UE supportsT312 operation on SCG as well. The following example using T312 is onlyan illustration and the timer name can be different (e.g., T314 orT315). The configuration of T312 for PSCell shall be provided as part ofmeasurement configuration. The configuration and value of T312 isprovided as part of measurement object configuration and the applicationof T312 is provided as part of reporting configuration. If T312 isconfigured for the UE on SCG, and measurement report is triggered whenT310 is running for a measurement object and reporting configurationthat are configured with T312, timer T312 is started as illustratedbelow.

5.5.4 Measurement report triggering

5.5.4.1 General

If security has been activated successfully, the UE

1> for each measId included in the measIdList within VarMeasConfig

. . .

-   -   2> if the triggerType is set to event, and if the corresponding        reportConfig does not include numberOfTriggeringCells, and if        the entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells for all measurements after layer 3 filtering taken during        timeToTrigger defined for this event within the VarMeasConfig,        while the VarMeasReportList does not include a measurement        reporting entry for this measId (a first cell triggers the        event):        -   3> include a measurement reporting entry within the            VarMeasReportList for this measId;        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -    3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;    -   2> if the triggerType is set to event, and if the corresponding        reportConfig does not include numberOfTriggeringCells, and if        the entry condition applicable for this event, i.e. the event        corresponding with the eventId of the corresponding reportConfig        within VarMeasConfig, is fulfilled for one or more applicable        cells not included in the cellsTriggeredList for all        measurements after layer 3 filtering taken during timeToTrigger        defined for this event within the VarMeasConfig (a subsequent        cell triggers the event):        -   3> set the numberOfReportsSent defined within the            VarMeasReportList for this measId to 0;        -   3> include the concerned cell(s) in the cellsTriggeredList            defined within the VarMeasReportList for this measId;        -   3> if the UE supports T312 and if useT312 is included for            this event and if T310 is running:            -   4> if T312 is not running:                -   5> start timer T312 with the value configured in the                    corresponding measObject;        -   3> initiate the measurement reporting procedure, as            specified in 5.5.5;

Timer T312 is stopped when handover command from the network, or when UEinitiates re-establishment message or when UE recovers from lower layerproblems as illustrated below:

5.3.5.4 Reception of an RRCConnectionReconfiguration including themobilityControlInfo by the UE (handover)

If the RRCConnectionReconfiguration message includes themobilityControlInfo and the UE is able to comply with the configurationincluded in this message, the UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

. . .

5.3.7 RRC connection re-establishment

5.3.7.2 Initiation

The UE shall only initiate the procedure either when AS security hasbeen activated or for a NB-IoT UE supporting RRC connectionre-establishment for the Control Plane CIoT EPS optimisation. The UEinitiates the procedure when one of the following conditions is met:

1> upon detecting radio link failure, in accordance with 5.3.11; or

1> upon handover failure, in accordance with 5.3.5.6; or

1> upon mobility from E-UTRA failure, in accordance with 5.4.3.5; or

1> upon integrity check failure indication from lower layers concerningSRB1 or SRB2; or

1> upon an RRC connection reconfiguration failure, in accordance with5.3.5.5; or

1> upon an RRC connection reconfiguration failure, in accordance withT538.331 [82, 5.3.5.5].

Upon initiation of the procedure, the UE shall:

1> stop timer T310, if running;

1> stop timer T312 on PCell, if running;

1> stop timer T313, if running;

1> stop timer T312 on PSCell, if running;

. . .

5.3.11.2 Recovery of physical layer problems

Upon receiving N311 consecutive “in-sync” indications for the PCell fromlower layers while T310 is running, the UE shall:

1> stop timer T310;

1> stop timer T312 for PCell, if running;

1> stop timer T310;

1> stop timer T312 for PSCell, if running;

. . .

5.4.3.3 Reception of the MobilityFromEUTRACommand by the UE

The UE (100) shall be able to receive a MobilityFromEUTRACommand messageand perform a cell change order to

GERAN, even if no prior UE measurements have been performed on thetarget cell.

The UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

5.3.10.10 SCG reconfiguration

The UE shall:

1> if makeBeforeBreakSCG is configured:

-   -   2> stop timer T313, if running;    -   2> stop timer T312, if running;

T312 Upon triggering a measurement Upon receiving N311 consecutive IfT312 is kept in MCG: report on SpCell, for a in-sync indications fromlower If security is not activated: measurement identity for layers forthe SpCell, upon go to RRC_IDLE else: initiate which T312 has beenreceiving RRCR econfiguration the connection re-establishmentconfigured, while T310 is with reconfigurationWithSync procedure runningon that SpCell for that cell group, upon If the T310 is kept in SCG,initiating the connection Inform E-UTRAN/NR about the re-establishmentprocedure, SCG radio link failure by and upon the expiry of T310.initiating the SCG failure Upon SCG release, if the informationprocedure as T312 is kept in SCG specified in 5.7.3.

When T312 expires, UE declares SCG radio link failure or SCG failure andinitiates recovery using SCG failure information procedure asillustrated below:

5.3.11.3 Detection of Radio Link Failure

. . .

In case of DC, the UE shall:

1> upon T313 expiry; or

1> upon T312 expiry on PSCell;

1> upon random access problem indication from SCG MAC; or

1> upon indication from SCG RLC, which is allowed to be sent on PSCell,that the maximum number of retransmissions has been reached for an SCGor split DRB:

-   -   2> consider radio link failure to be detected for the SCG i.e.        SCG-RLF;    -   2> initiate the ure information procedure as specified in 5.6.13        to report SCG radio link failure;

In case of CA PDCP duplication, the UE shall:

1> upon indication from an RLC entity, which is restricted to be sent onSCell only, that the maximum number of retransmissions has been reached:

-   -   2> consider radio link failure to be detected for the RLC        entity;    -   2> initiate the failure information procedure as specified in        5.6.21 to report PDCP duplication failure;

The UE may discard the radio link failure information, i.e. release theUE variable VarRLF-Report, 48 hours after the radio link failure isdetected, upon power off or upon detach.

T314 Upon triggering a measurement Upon receiving N313 consecutiveInform E-UTRAN/NR about report on PSCell, for a in-sync indications fromlower the SCG radio link failure measurement identity for layers for thePSCell, upon by initiating the SCG which T314 has been receivinghandover command for failure information procedure configured, whileT313 is that cell group, upon initiating as specified in 5.7.3. runningon that PSCell the connection re-establishment procedure, and upon theexpiry of T313. Upon SCG release or NE-DC release,

In an embodiment, NR-DC, procedural text from TS 38.331 for NR SA isapplicable for NR MCG, procedural text from TS 38.331 for NR SCG isapplicable. In an embodiment, Method of handling T312 in NR-DCoperations, Method of handling T312 on NR MCG/PCell in NR-DC operations(3GPP TS 38.331), Handling of T312 and operations based on T312 state onNR MCG or PCell in NR-DC operation is similar to that of NR standaloneoperation as illustrated in earlier section. The same operations andprocedure for measurement report triggering, start, stop and expiry ofT312 is applicable here.

T312 Upon triggering a measurement Upon receiving N311 consecutive IfT312 is kept in MCG: report on SpCell, for a in-sync indications fromlower If security is not activated: measurement identity for layers forthe SpCell, upon go to RRC_IDLE else: initiate which T312 has beenreceiving RRCReconfiguration the connection re-establishment configured,while T310 is with reconfigurationWithSync procedure running on thatSpCell for that cell group, upon If the T310 is kept in SCG, initiatingthe connection Inform E-UTRAN/NR about the re-establishment procedure,SCG radio link failure by and upon the expiry of T310. initiating theSCG failure Upon SCG release, if the information procedure as T312 iskept in SCG specified in 5.7.3.

In an embodiment, Method of handling T312 on NR SCG/PSCell in NE-DCoperations (3GPP TS 38.331), Handling of T312 and operations based onT312 state on NR SCG or PSCell in NR-DC operation is similar to thehandling of T312 on NR SCG when operating in (NG) EN-DC operation asillustrated in earlier section. The same operations and procedure formeasurement report triggering, start, stop and expiry of T312 isapplicable here.

In an example, at S202 b, the SN (300) sends the measurementconfiguration to the UE (100). At S204 b, the data from SN bearers isestablished between the UE (100) and the SN (300). At S206 b, the SN(300) sends the RRC reconfiguration to the UE (100). At S208 b, the UE(100) detects the Qout for the PSCell. At S210 a, the UE (100) startsthe timer (i.e., T310) for the PScell. At S212 a, the UE (100) sends themeasurement report to the SN (300) over the SRB3 message. At S214 b, theUE (100) starts the second timer (i.e., T312), the second timer isexpired and the first timer is stopped. At S216 b, the UE (100)initiates the SCG failure procedure. At S218 b, the UE (100) shares theSCG failure information to the MeNB (200). At S220 b, the MeNB (200)initiates the SCG failure recovery actions.

FIG. 3A is a flow diagram illustrating a method for attempting cellselection on LTE (or the next priority RAT) On T310 expiry, according toan embodiment as disclosed herein.

In an embodiment, method can be used to detect the RLF using the T312,for IRAT measurement reporting. The methods explained earlier arerelated to early SCG failure detection and indication in dualconnectivity scenario. This feature is useful also in a singleconnectivity scenario as well. Currently, T312 based early RLF detectionis primarily used in intra-RAT coverage boundaries. With theintroduction of NR technology, existing LTE networks are expected to beupgraded in order to support NR operation. However, NR service is notavailable at every location. Early deployments of integrating NR overexisting LTE networks is to provide NR services in selected areas. Thedeployments are as hotspots for providing improved broadband service tothe subscriber while maintaining the existing LTE RF footprint forproviding coverage once the UE moves away from these NR availableregions. Therefore, the NR coverage is expected to be sparse. As aresult, there arise a case where a UE in connected state in NR is unableto sustain the channel and there are no NR neighbor cells available. UEeventually satisfies Qout criteria and T310 is started. On T310 expiry,the UE will attempt recovery on NR first, the failure of which wouldresult in attempting cell selection on LTE (or the next priority RAT) asillustrated in FIG. 3A.

In an example, at S302 a, the UE (100) acquires the measurementconfiguration from the source gNB (i.e., NR). At 304 a, data and controlpath is established between the UE (100) and the source gNB (i.e., NR).At 306 a, the UE (100) determines that Qout is satisfied for servicingcell. At S308 a, the first timer (i.e., T310) is started for theservicing cell. At S310 a, the UE (100) sends the IRAT measurementreport to the source gNB (i.e., NR). At S312 a, the T310 is expired andUE (100) declares the RLF. At S314 a, the UE (100) initiates the cellselection procedures. At S316 a, the UE (100) does not select the NRsuitable cells and selects the LTE cell. At S318 a, the UE (100) sendsthe RRC connection request to the target eNB (i.e., LTE).

FIG. 3B is a flow diagram illustrating a method for the mobility from NRor handover to LTE command from the network may not be receivedeventually leading to RLF due to T310 expiry, according to an embodimentas disclosed herein.

In such a scenario where only LTE neighbor cells are available and theUE has triggered an IRAT measurement report for LTE neighbor cells, theUE is aware that an LTE cell suitable of handling service is availablein vicinity. However, since the UE is in out of sync state, the mobilityfrom NR or handover to LTE command from the network may not be receivedeventually leading to RLF due to T310 expiry. If T312 is configured forIRAT measurement objects, the UE would start T312 once the IRATreporting criteria is satisfied and measurement report is sent to thenetwork. On expiry of T312, UE would declare early RLF and attempt forfaster recovery on the LTE cell. This recovery may be by attempting LTEcell search on RLF declaration using the knowledge that the UE hasidentified only LTE cells to be in its coverage. Otherwise, RLF recoverymay first be attempted on NR and if no suitable cells are found, it mayattempt on LTE cells. In such a scenario UE instead of performing RRCre-establishment on the LTE cell will attempt connection establishmentby sending the RRC connection request message. T312 configuration in NRfor IRAT may use a UE specific timer value configuration as part of SIB1carrying ue-timersAndconstants or using measurement object specificconfiguration as illustrated below:

T312 configuration using ue-timersAndConstants in SIB1:

UE-TimersAndConstants ::= SEQUENCE { t300  ENUMERATED {ms100, ms200,ms300, ms400, ms600, ms1000, ms1500, ms2000}, t301  ENUMERATED {ms100,ms200, ms300, ms400, ms600, ms1000, ms1500, ms2000}, t310  ENUMERATED{ms0, ms50, ms100, ms200, ms500, ms1000, ms2000}, n310  ENUMERATED {n1,n2, n3, n4, n6, n8, n10, n20}, t311  ENUMERATED {ms1000, ms3000, ms5000,ms10000, ms15000, ms20000, ms30000}, n311  ENUMERATED {n1, n2, n3, n4,n5, n6, n8, n10}, t319  ENUMERATED {ms100, ms200, ms300, ms400, ms600,ms1000, ms1500, ms2000}, t312 ENUMERATED {ms0, ms50, ms100, ms200,ms300,ms400, ms500, ms1000}, ... }

T312 configuration in IRAT measurement object configuration on NR(MeasObjectEUTRA):

MeasObjectEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValueEUTRA,allowedMeasBandwidth AllowedMeasBandwidth, ... t312-Config-r16SetupRelease { T312-Config ) OPTIONAL NEED N ... } T312-Config SEQUENCE{ release NULL, setup ENUMERATED {ms0, ms50, ms100, ms200, ms300, ms400,ms500, ms1000} }

or

MeasObjectEUTRA ::= SEQUENCE { carrierFreq ARFCN-ValucEUTRA,allowedMeasBandwidth AllowedMeasBandwidth, ... t312-r16 ENUMERATED {ms0,ms50, ms100, ms200, ms300, ms400, ms500, ms1000} OPTIONAL, -- Need R ...}

Going forward, NR is expected to be deployed with both operationalfrequencies deployed (FR1 i.e. below 6 GHz and FR2 i.e. above 6 GHz) ina heterogeneous deployment where there are plenty of small pico cellsdeployed on FR2 along with large macro cells on FR1. There can belocations where only NR coverage is available and LTE cells are notsuitable. In future, the operators may migrate the LTE cells connectedto EPC to eLTE cells which are capable to operate with 5GC (5G Corenetwork, NR core network). The support of EPC may be discontinued inorder for the operator to maintain a single core network. It is possiblethat NR coverage is available in areas where LTE coverage is notpresent. Also, the FR2 cells which are of small coverage and very highbandwidth will be densely deployed in order to provide NR services andimproved mobile broadband to the users. It is possible that these smallcoverage cells are going to be in coverage of otherwise coverage holes.Therefore, it is possible that a UE operating on LTE might only have aneighbour NR cells which is suitable (in good signal conditions) andcapable of providing service to the UE. Therefore, it is required thatT312 based early RLF detection is allowed for IRAT measurement reportsas well. T312 configuration in LTE system shall be supported for IRAT NRmeasurement objects as illustrated below,

IRAT NR reporting from EUTRAN serving cell:

MeasObjectNR-r15 ::= SEQUENCE { carrierFreq-r15 ARFCN-ValueNR-rl5,rs-ConfigSSB-r15 RS-ConfigSSB-NR-r15, threshRS-Index-r15ThresholdListNR-r15 OPTIONAL, -- Need OR ... t312-r16 CHOICE { releaseNULL, setup ENUMERATED {ms0, ms50. ms100, ms200, ms300, ms400, ms500,ms1000} } OPTIONAL, -- Need ON ... *208 ^(})

The UE (100) can be configured to apply T312 based configuration basedon network configuring the application of T312 in reportingconfiguration IRAT measurements i.e. events B1 and B2. Different optionsof signalling the application. The application of T312 for a particularmeasurement report is based on the indication of T312 requirement forthe configured reporting configuration. For EUTRA reportingconfigurations when connected to NR cell, T312 usage may be configuredas a common IE which can be applied for any reporting configurationwithin the EventTriggerConfig as illustrated below:

EventTriggerConfigInterRAT ::= SEQUENCE { eventId  CHOICE { eventB1SEQUENCE { b1-ThresholdEUTRA MeasTriggerQuantityEUTRA, reportOnLeave BOOLEAN, hysteresis Hysteresis, timeToTrigger TimeToTrigger, ... },eventB2 SEQUENCE { b2-Thrcshold1 MeasTriggerQuantity, b2-Threshold2EUTRAMeasTriggerQuantityEUTRA, reportOnLeave  BOOLEAN, hysteresis Hysteresis,timeToTrigger TimeToTrigger, ... }, ... }, rsType NR-RS-Type,reportInterval ReportInterval, reportAmount  ENUMERATED {r1, r2, r4, r8,r16, r32, r64, infinity}, reportQuantity MeasReportQuantity,maxReportCells  INTEGER (1..maxCellReport),  useT312 BOOLEAN OPTIONAL,-- Need N ... }

Alternatively, T312 usage can be signaled as a measurement eventspecific configuration within the EventTriggerConfig as illustratedbelow:

EventTriggerConfigInterRAT ::= SEQUENCE { eventId  CHOICE { eventB1SEQUENCE { b1-ThresholdEUTRA MeasTriggerQuantityEUTRA, reportOnLeave BOOLEAN, hysteresis Hysteresis, timeToTrigger  TimeToTrigger, useT312BOOLEAN  OPTIONAL, -- Need N ... }, eventB2 SEQUENCE { b2-Threshold1 MeasTriggerQuantity, b2-Threshold2EUTRA MeasTriggerQuantityEUTRA,reportOnLeave  BOOLEAN, hysteresis Hysteresis, timeToTrigger TimeToTrigger, useT312 BOOLEAN  OPTIONAL, -- Need N ... }, ... },rsType NR-RS-Type, reportInterval  ReportInterval, reportAmount ENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity}, reportQuantityMeasReportQuantity, maxReportCells INTEGER (1..maxCellReport), ... }

Similarly, for reporting configuration of NR frequencies when connectedto EUTRA, T312 usage may be configured as a common IE which can beapplied for any reporting configuration within the ReportConfigInterRATas illustrated below:

ReportCoaftgInterRAT ::=  SEQUENCE { triggerType  CHOICE {  eventSEQUENCE { eventId  CHOICE { eventB1 SEQUENCE { b1-Threshold CHOICE {b1-ThresholdUTRA ThresholdUTRA, b1-ThresholdGERAN ThresholdGERAN,b1-ThresholdCDMA2000 ThresholdCDMA2000} }, eventB2 SEQUENCE {b2-Threshold1 ThresholdEUTRA, b2-Threshold2 CHOICE { b2-Threshold2UTRAThresholdUTRA, b2-Threshold2GERAN ThreshoklGERAN, b2-Threshold2CDMA2000ThresholdCDMA2000 } }, ..., eventW1-r13 SEQUENCE { w1-Threshold-r13WLAN-RSSI-Range-r13 }, eventW2-r13 SEQUENCE { w2-Threshold1-t13 WLAN-RSSI-Range-r13, w2-Threshold2-r13  WLAN-RSSI-Range-r13 },eventW3-r13 SEQUENCE { w3-Threshold-r13  WLAN-RSSI-Range-r13 },eventB1-NR-r15 SEQUENCE { b1-ThresholdNR-r15 ThresholdNR-r15,reportOnLeave-r15 BOOLEAN }, eventB2-NR-r15 SEQUENCE { b2-Threshold1-r15ThresholdEUTRA, b2-Threshold2NR-r15 ThresholdNR-r15, reportOnLeave-r15BOOLEAN } }, hysteresis Hysteresis, timeToTrigger TimeToTrigger  }, periodical SEQUENCE { purpose ENUMERATED { reportStrongestCells,reportStrongestCellsForSON,  reportCGI}  }  },  maxReportCells INTEGER(1..maxCellReport),  reportInterval ReportInterval,  reportAmountENUMERATED {r1, r2, r4, r8, r16, r32, r64, infinity},  ...,  [[si-RequestForHO-r9 ENUMERATED {setup} OPTIONAL -- Cond reportCGI]],  [[reportQuantityUTRA-FDD-r10 ENUMERATED {both} OPTIONAL -- Need OR]],  [[includeLocationInfo-r11 BOOLEAN  OPTIONAL -- Need ON]],  [[b2-Thresholdl-v1250  CHOICE { release NULL, setup RSRQ-Range-v1250  }OPTIONAL -- Need ON  ]],  [[ reportQuantityWLAN-r13ReportQuantityWLAN-r13 OPTIONAL -- Need ON]],  [[ reportAnyWLAN-r14BOOLEAN OPTIONAL -- Need ON]],  [[ reportQuantityCellNR-r15ReportQuantityNR-r15 OPTIONAL, -- Need ON  maxReportRS-Index-r15 INTEGER(0..maxRS-IndexReport-r15) OPTIONAL,  -- Need ON reportQuantityRS-IndexNR-r15 ReportQuantityNR-r15 OPTIONAL, -- Need ON reportRS-IndcxResultsNR BOOLEAN OPTIONAL, -- Need ON reportSFTD-Mcas-r15 ENUMERATED {pSCell, neighborCells } OPTIONAL  --Need ON  useT312 BOOLEAN OPTIONAL, -- Need ON  ]]

At 302 b, the UE (100) acquires the measurement configuration from thesource gNB (i.e., LTE). At 304 b, data and control path is establishedbetween the UE (100) and the source gNB (i.e., LTE). At 306 b, the he UE(100) determines that Qout is satisfied for servicing cell. At 308 b,the first timer (i.e., T310) is started for the servicing cell. At 310b, the UE (100) sends the IRAT measurement report to the source gNB(i.e., LTE). At 312 b, the T310 is expired and UE (100) declares theRLF. At 314 b, the UE (100) initiates the cell selection procedures. At316 b, the UE (100) does not select the LTE cells and selects the NRcell. At 318 b, the UE (100) sends the RRC setup request to the targeteNB (i.e., NR).

FIG. 4A is a flow diagram illustrating a method for enables the UE torecover from service interruption by allowing the UE to performconnection establishment on the target cell faster than the case whereT312 is not applied, according to an embodiment as disclosed herein.

After selecting a suitable cell on the target RAT (LTE cell in case ofT312 expiry on NR or NR cell in case of T312 expiry on LTE), the UE doesnot perform re-establishment since the target cell cannot retrieve theUE context and the UE cannot re-establish to target RAT. As a result,the UE performs new connection establishment. This method enables the UEto recover from service interruption by allowing the UE to performconnection establishment on the target cell faster than the case whereT312 is not applied. This procedure is illustrated in FIG. 4A.

In an example, at S402 a, the UE (100) acquires the measurementconfiguration from the source gNB (i.e., NR). At S404 a, data andcontrol path is established between the UE (100) and the source gNB(i.e., NR). At S406 a, the UE (100) determines that Qout is satisfiedfor the servicing cell. At S408 a, the first timer (i.e., T310) isstarted for the servicing cell. At S410 a, the UE (100) sends themeasurement report to the source gNB (i.e., NR). At S412 a, the T310 isexpired, T310 is stopped and UE (100) declares the RLF. At S414 a, theUE (100) initiates the cell selection procedures. At S416 a, the UE(100) does not select the NR suitable cells and selects the LTE cell. At418 a, the UE (100) sends the RRC connection request to the target eNB(i.e., LTE).

FIG. 4B is a flow diagram illustrating a method for send RRC setuprequest from Source eNB (LTE) to Target gNB (NR) on T312 expire,according to an embodiment as disclosed herein.

In an example, at 402 b, the UE (100) acquires the measurementconfiguration from the source gNB (i.e., LTE). At 404 b, data andcontrol path is established between the UE (100) and the source gNB(i.e., LTE). At 406 b, the UE (100) determines that Qout is satisfiedfor servicing cell. At 408 b, the first timer (i.e., T310) is startedfor the servicing cell. At S410 b, the UE (100) sends the measurementreport to the source gNB (i.e., LTE). At S412 b, the T310 is expired andUE (100) declares the RLF. At 414 b, the UE (100) initiates the cellselection procedures. At 416 b, the UE (100) does not select the LTEcells and selects the NR cell. At 418 b, the UE (100) sends the RRCsetup request to the target eNB (i.e., NR).

FIG. 5 is a flow diagram illustrating a method to stop T312 onsatisfying leaving condition, according to an embodiment as disclosedherein.

In an embodiment, method to handle T312 on satisfying leaving conditionof a reporting configuration. As seen earlier, T312 is started once T310is running on the UE and a measurement report is triggered for an eventconfigured to use T312. On T312 expiry, UE declares early RLF on PCellor SCG failure (i.e. early RLF on PSCell) and attempts for recovery.However, it is possible that the UE satisfies leaving condition of theevent that triggered measurement report while T312 is running. This mayhappen either due to improvement in serving cell signal conditions ordue to degradation of neighbor cell signal conditions.

In an embodiment, the method can be used to stop T312 on satisfyingleaving condition, if the leaving condition is satisfied due toimprovement in serving cell conditions, it is likely that the UE willreturn to in-sync state and can continue operating on the serving cellfurther. This case arise when the signal condition of the serving celltemporarily degraded due to any of short term fading or interferencetowards the cell edge and not necessarily because the UE is movingtowards the edge of coverage of the serving cell and towards a neighborcell coverage. There is a good probability that UE recovers the signalconditions and can sustain the radio link. In such a case, the UE canreceive the handover message from the network instead of declaring anearly RLF and performing recovery procedures. Therefore, it is proposedthat the UE stops T312 when the UE satisfies the leaving condition of areporting configuration for which a measurement report was transmittedto the network earlier (This is the MR that triggered the start of timerT312).

Similarly, if leaving condition is satisfied due to degradation in theneighbor cell signal conditions, it is likely that the neighbor cellchannel is not strong to sufficiently handle the UE once connected toit. In such cases, it is optimal to provide the UE with increasedopportunity of recovering the serving cell by monitoring for in-syncindications. Since the leaving condition for the frequency has beensatisfied due to degradation of neighbor cell signal conditions, thereis no gain in declaring early RLF and attempting fast recovery as thisneighbor cell may no longer be suitable. As a result, stopping T312 onsatisfying the leaving condition will provide the UE with moreopportunity to monitor in-sync from the serving cell as well asmonitoring for other neighbor cells for which measurement reportingentry condition is satisfied and T312 may be started.

Therefore, it may benefit the UE if the timer T312 is stopped when theleaving condition for measurement configuration which started T312 issatisfied. The UE need to ensure that there is no other measurementreport sent to the network when T310 is running and use-T312 isconfigured. If there are other measurement reports that are also sent tothe network when T310 is running, UE will stop T312 only if this is thelast measurement (no other measurements are still satisfying the entrycondition of a reported MR) for which T312 was configured. The UEprocedures based on stopping T312 when the leaving condition issatisfied is illustrated in FIG. 5.

In an example, at S502, the UE (100), in the connected state, performsthe RLM. At S504, the UE (100) determines whether the NT310/Qout issatisfied? If NT310/Qout is not satisfied then, the method performs stepof 502 a. If the NT310/Qout is satisfied then, the UE (100) starts T310at S506 a. At S508 a, the UE (100) monitors for in sync indication. AtS510 a, the UE determines whether the MR triggers with T312. If the MRtriggers with T312 then, the UE (100) starts/restarts T310 at S512 a. Ifthe MR does not trigger with T312 then the UE (100) monitors for in syncindication at S516 a.

At 514 a, the UE (100) determines that MR leaves the condition. If theMR leaves the condition then, the UE (100) starts/restarts T310 at S512a. If the MR does not leave the condition then, the method performssteps at S516 a. At 518 a, the UE (100) determines the T312 expiry andT310 expiry. If the T312 is not expired and T310 is not expired then,the method performs steps at S508 a. If the T312 is expired and T310 isexpired then, the UE (100) declares the RLF/SCG failure at S522 a. AtS524 a, the method performs the recovery procedure.

FIG. 5B is a flow diagram illustrating a method to restart T312 onsatisfying leaving condition, according to an embodiment as disclosedherein.

In an example, at S502 b, the UE (100), in the connected state, performsthe RLM. At S504 b, the UE (100) determines whether the NT310/Qout issatisfied? If NT310/Qout is not satisfied then, the method performs stepof 502 b. If the NT310/Qout is satisfied then, the UE (100) starts T310at S506 b. At S508 b, the UE (100) monitors for in sync indication. AtS510 b, the UE determines whether the MR triggers with T312. If the MRtriggers with T312 then, the UE (100) starts/restarts T310 at S512 b. Ifthe MR does not trigger with T312 then the UE (100) monitors for in syncindication at S518 b.

At 514 b, the UE (100) determines that MR leaves the condition. If theMR leaves the condition then, the UE (100) stops the T312 at S516 b. Ifthe MR does not leave the condition then, the method performs steps atS518 b. At 520 b, the UE (100) determines the T312 expiry and T310expiry. If the T312 is not expired and T310 is not expired then, themethod performs steps at S508 b. If the T312 is expired and T310 isexpired then, the UE (100) declares the RLF/SCG failure at S522 b. AtS524 b, the method performs the recovery procedure.

In an embodiment, method can be used to restart T312 on satisfyingleaving condition. If the leaving condition is satisfied due toimprovement in serving cell conditions, then the UE needs to ensure thatthis is not a momentary change as there is no time to triggerconfiguration associated while monitoring the leaving criteria of anevent. It is possible that the serving cell measurement result indicatedan improvement only during one measurement occasion and again satisfiedthe entering criteria in the next measurement occasion leading to afrequent fluctuating measurement at the UE. Stopping T312 during thefirst occasion where it satisfied the leaving criteria would result inthe UE starting T312 at a later point in time when the entry criteria issatisfied again. This leads to UE being in out of sync state for longerduration than required and may work against the objective of early RLFdeclaration. If the serving cell signal conditions have actuallyimproved due to which leaving condition was satisfied, it provides theUE to continue normal operation and will likely return to in sync state.The probability of correctly receiving the handover command from thenetwork also increases. Continuing T312 when the leaving condition issatisfied would leave the UE with less time and small occasion toreceive handover message from the network and to return to in-syncstate.

Similarly, if leaving condition is satisfied due to degradation in theneighbor cell signal conditions, the UE needs to ensure that this is nota momentary change as there is no time to trigger configurationassociated while monitoring the leaving criteria of an event. It ispossible that the neighbor cell measurement result indicated adegradation only during one measurement occasion and again satisfied theentering criteria in the next measurement occasion leading to a frequentfluctuating measurement at the UE. Stopping T312 during the firstoccasion where it satisfied the leaving criteria would result in the UEstarting T312 at a later point in time when the entry criteria issatisfied again. This leads to delay in declaring RLF when UE is in astate where there is a neighbor cell available and the serving cell isnot improving. This may as well work against the objective of havingearly RLF detection. Had the neighbor cell signal conditions actuallydegraded, then continuing the timer would result in a state where the UEdeclares RLF but did not have any suitable cell to recover on. This alsoleads to reducing the UE opportunity of returning to in-sync with theserving cell which may be more probable as there are no neighbors inthat area anyway.

Therefore, stopping T312 or continuing T312 during the event of a UEsatisfying the leaving condition of a measurement event that triggeredthe start of T312 does not appear to the most suitable solution as it isdependent on the nature of signal and channel conditions that lead tothose events. A more plausible approach is to come up with an approachwhich provides better probability of early RLF detection with reducedprobability of entering into error scenarios that UE would encounter bystopping or continuing T312. Therefore, it is proposed that the UErestarts T312 when the leaving condition is first met. This way, if thechange in signal condition was momentary, the UE will not have torestart the timer later and stay in the weak serving cell for a longduration. If the change in measurements are actually due to change insignal conditions, then this give added opportunity to receive handovermessage from the network thereby providing an opportunity of continuingservice without interruption. Therefore, it may benefit the UE if thetimer T312 is restarted when the leaving condition for measurementconfiguration which started T312 is satisfied. The UE need to ensurethat there is no other measurement report sent to the network when T310is running and use-T312 is configured. If there are other measurementreports that are also sent to the network when T310 is running, UE willrestart T312 only if this is the last measurement (no other measurementsare still satisfying the entry condition of a reported MR) for whichT312 was configured. The sequence of procedures involved is illustratedin the flowchart on FIG. 5 b.

In either of the cases where T312 is either stopped or restarted onsatisfying the meeting criteria, it is imperative that the networkconfigures repot on leave for the measurement reporting configurationsrequired to use T312. This is essential so that the network is awarethat the neighbor cell earlier reported is not strong enough forhandover. This way, when the next time an event is satisfied, the UEwill report the measurement report to the network and network caninitiate handover with the latest and most correct measurementavailable.

In an embodiment, method to indicate the support of T312 in MRDC andIRAT is introduced. The network nodes should be aware of whether the UEsupport T312 based operation in MCG Only or SCG only or on both. Thenetwork nodes also need to be made aware of whether the UE supports T312operation for IRAT measurement reporting as well.

In an embodiment, method to indicate to EUTRAN about the UE support ofT312 or T314 or T315 timer for controlling early SCG RLF or SCG failuredeclaration is introduced for NE-DC. In LTE, there is already T312defined in specification 3GPP TS 36.306 and 36.331 for handling of earlyRLF declaration or fast handover recovery mechanism. However, this is afeature from old release and reusing the same for SCG recovery may leadto backward compatibility issues. Therefore, a new timer say T314 orT315 has to be introduced in LTE to indicate the support of early SCGRLF declaration and fast SCG handover recovery. Otherwise, T312 may becommonly used to control early RLF declaration on both MCG and SCG. Insuch cases, a new UE capability for indicating support of T312 on SCGneed to be sent to the network to make network aware that UE supportsT312 operation on SCG as well. The following example using T314 is onlyan illustration and the timer name can be different (e.g.: T312 orT315). The UE capability is indicated to the network as illustratedbelow. The capability may also be indicated using a suffix/extension toT312 capability (e.g.: T312-SCG).

In 3GPP TS 36.306:

4.3.6.x timerT314-r16

This field defines whether the UE supports T314 as specified in TS36.331[5]

In 3GPP TS 36.331:

UE-EUTRA-Capability-v1530-IEs ::= SEQUENCE { measParameters-v1530MeasParameters-v1530 OPTIONAL, otherParameters-v1530Other-Parameters-v1530 OPTIONAL, neighCellSI-AcquisitionParameters-v1530NeighCellSI-AcquisitionParameters-v1530 OPTIONAL, mac-Paramctcrs-v1530MAC-Paramctcrs-v1530 OPTIONAL, phyLayerParameters-v1530PhyLayerParameters-v1530 OPTIONAL, rf-Parameters-v1530RF-Parameters-v1530 OPTIONAL, pdcp-Parameters-v1530PDCP-Parameters-v1530 OPTIONAL, ue-CategoryDL-v1530 INTEGER (22..26)OPTIONAL, ue-BasedNetwPerfMeasParameters-v1530UE-BasedNetwPerfMeasParameters-v1530 OPTIONAL, rlc-Parameters-v1530RLC-Parameters-v1530 OPTIONAL, sl-Parameters-v1530 SL-Parameters-v1530OPTIONAL, extendedNumberOfDRBs-r15 ENUMERATED {supported} OPTIONAL,reducedCP-Latency-r15 ENUMERATED {supported} OPTIONAL,laa-Parameters-v1530 LAA-Parameters-v1530 OPTIONAL, ue-CategoryUL-v1530INTEGER (22..26) OPTIONAL, fdd-Add-UE-EUTRA-Capabilities-v1530UE-EUTRA-CapabilityAddXDD-Mode-v1530 OPTIONAL,tdd-Add-UE-EUTRA-Capabilities-v1530 UE-EUTRA-CapabilityAddXDD-Mode-v1530OPTIONAL, nonCriticalExtension UE-EUTRA-Capability-v1610-IEs OPTIONAL }UE-EUTRA-Capability-v1610-IEs ::= SEQUENCE { measParameters-v1610MeasParameters-v1610 OPTIONAL, nonCriticalExtension SEQUENCE { }OPTIONAL }

In an embodiment, method to indicate to NR about the UE support of T312timer for controlling early RLF in NR SA and NR-DC scenarios. In anembodiment, method to indicate to NR about the UE support of T312 timerfor controlling early SCG RLF or SCG failure declaration is introducedfor (NG) EN-DC. There are two ways in which this capability can beindicated to the network. One method is to indicate to the network as acommon IE indicating support of T312 operation on both MCG as SCG.Another way of indicating to the network is as independent supportindications (separate IEs) for T312 support of MCG and SCG. Both themethods are illustrated below:

FDD-TDD FR1 FR2 Definitions for parameters Per M diff diff csi-RS-RLM UEYes No Yes Indicates whether the UE can perform radio link monitoringprocedure based on measurement of CSI-RS as specified in TS38.213 [11]and TS38.133 [5| This parameter needs FR1 and FR2 differentiation.csi-RSRP-AndRSRQ-MeasWithSSB UE No No Yes. indicates whether the UE canperform CSI- RSRP and CSI-RSRQ measurement as specified in TS38.215[13], where CSI-RS resource is configured with an associated SS/PBCH.This parameter needs FR1 and FR2 differentiation.csi-RSRP-AndRSRQ-MeasWithoutSSB UE No No Yes Indicates whether the UEcan perform CSI- RSRP and CSI-RSRQ measurement as specified in TS38.215[13], where CSI-RS resource is configured for a cell that transmitsSS/PBCH block and without an associated SS/PBCH block. This parameterneeds FR1 and FR2 differentiation. csi-SINR-Meas UE No No Yes Indicateswhether the UE can perform CSI- SINR measurements based on configuredCSI- RS resources as specified in TS38.215 [13]. This parameter needsFR1 and FR2 differentiation. eventA-MeasAndReport UE Yes Yes NoIndicates whether the UE supports NR measurements and events A triggeredreporting as specified in TS 38.331 [9] independentGapConfig UE No YesNo This field indicates whether the UE supports two independentmeasurement gap configurations for FR1 and FR2 specified in TS 38.133[5]. intraAndInterF-MeasAndReport UE Yes Yes No Indicates whether the UEsupports NR intra- frequency and inter-frequency measurements and atleast periodical reporting. simultaneousRxDataSSB-DiffNumerology UE TbdYes Yes Indicates whether the UE supports concurrent intra-frequencymeasurement on serving cell or neighbouring cell and PDCCH or PDSCHreception from the serving cell with a different numerology.sftd-MeasPSCell UE No Yes No Indicates whether the UE supports SFTDmeasurements between the Pcell and a configured PSCell. sftd-MeasNR-CellUE No Yes No Indicates whether the SFTD measurement between the Pcelland the NR cells is supported by the UE which is capable of EN-DC whenEN-DC is not configured. ss-SINR-Meas UE No No Yes Indicates whether theUE can perform SS- SINR measurement as specified in TS38 215 [13] Thisparameter needs FR1 and FR2 differentiation. supportedGapPattern UE NoNo No Indicates measurement gap pattern(s) optionally supported by theUE. The leading/ leftmost bit (bit 0) corresponds to the gap pattern 2,the next bit corresponds to the gap pattern 3, as specified in TS 38.311[9] and so on. T312 UE No No No Indicates if the UE supports RLFdeclaration on MCG and SCG when T312 is expired

or

FDD-TDD FR1 FR2 Definitions for parameter» Per M diff diff csi-RS-RLM UEYes No Yes Indicates whether the UE can perform radio link monitoringprocedure based on measurement of CSI-RS as specified in TS38.213 [11]and 38.133 [5]. This parameter needs FR1 and FR2 differentiation.csi-RSRP-AndRSRQ-MeasWithSSB UE No No Yes Indicates whether the UE canperform CSI- RSRP and CSI-RSRQ measurement as specified in TS38.215[13], where CSI-RS resource is configured with an associated SS/PBCH.This parameter needs FR1 and FR2 differentiation.csi-RSRP-AndRSRQ-MeasWithoutSSB UE No No Yes Indicates whether the UEcan perform CSI- RSRP and CSI-RSRQ measurement as specified in TS38.215[13], where CSI-RS resource is configured for a cell that transmits SS/PBCH block and without an associated SS/ PBCH block. This parameterneeds FR1 and FR2 differentiation. csi-SINR-Meas UE No No Yes Indicateswhether the UE can perform CSI- SINR measurements based on configuredCSI- RS resources as specified in TS38.215 [13]. This parameter needsFR1 and FR2 differentiation. eventA-MeusAndReport UE Yes Yes NoIndicates whether the UE supports NR measurements and events A triggeredreporting as specified in TS 38.331 [9] independentGapConfig UE No YesNo This field indicates whether the UE supports two independentmeasurement gap configurations for FR1 and FR2 specified in TS 38.133[5] intraAndInterF-MeasAndReport UE Yes Yes No Indicates whether the UEsupports NR intra- frequency and inter-frequency measurements and atleast periodical reporting. simultaneousRxDataSSB-DiffNumerology UE TbdYes Yes Indicates whether the UE supports concurrent intra-frequencymeasurement on serving cell or neighbouring cell and PDCCH or PDSCHreception from the serving cell with a different numerologysftd-MeasPSCell UE No Yes No Indicates whether the UE supports SFTDmeasurements between the Pcell and a configured PSCell. sftd-MeasNR-CellUE No Yes No Indicates whether the SFTD measurement between the Pcelland the NR cells is supported by the UE which is capable of EN-DC whenEN-DC is not configured. ss-SINR-Meas UE No No Yes Indicates whether theUE can perform SS- SINR measurement as specified in TS38.215 [13]. Thisparameter needs FR1 and FR2 differentiation. supportedGapPattern UE NoNo No Indicates measurement gap pattern(s) optionally supported by theUE. The leading/leftmost bit (bit 0) corresponds to the gap pattern 2,the next bit corresponds to the gap pattern 3, as specified in TS 38.311[9] and so on. T312 UE No No No Indicates if the UE supports RLFdeclaration on MCG when T312 is expired T312-SCG UE No No No Indicatesif the UE supports SCG RLF or SCG failure declaration on SCG when T312is expired

MeasAndMobParamctersCommon ::= SEQUENCE { supportedGapPattern BIT STRING(SIZE (22)) OPTIONAL, ssb-RLM  ENUMERATED {supported}  OPTIONAL,ssb-AndCSI-RS-RLM  ENUMERATED {supported} OPTIONAL, T312 ENUMERATED{supported} OPTIONAL, ..., [[ eventB-MeasAndReport ENUMERATED{supported} OPTIONAL, handoverFDD-TDD  ENUMERATED {supported} OPTIONAL,eutra-CGI-Reporting ENUMERATED {supported}  OPTIONAL, nr-CGI-ReportingENUMERATED {supported}  OPTIONAL ]], [[ independentGapConfig  ENUMERATED{supported} OPTIONAL, periodicEUTRA-MeasAndReport  ENUMERATED{supported} OPTIONAL, handoverFR1-FR2 ENUMERATED {supported} OPTIONAL,maxNumberCSI-RS-RRM-RS-SINR ENUMERATED {n4, n8, n16, n32, n64, n96}OPTIONAL ]], }

or

MeasAndMobParametersCommon ::= SEQUENCE { T312 ENUMERATED {supported}OPTIONAL, ..., }

or

MeasAndMobParametersCommon ::=  SEQUENCE { supportedGapPattern BITSTRING (SIZE (22)) OPTIONAL, ssb-RLM  ENUMERATED {supported}  OPTIONAL,ssb-AndCSI-RS-RLM  ENUMERATED {supported} OPTIONAL, T312 ENUMERATED{supported} OPTIONAL, T312-SCG ENUMERATED {supported} OPTIONAL, ..., [[eventB-MeasAndReport  ENUMERATED {supported} OPTIONAL, handoverFDD-TDD ENUMERATED {supported} OPTIONAL, eutra-CGI-Reporting ENUMERATED{supported} OPTIONAL, nr-CGI-Reporting ENUMERATED {supported} OPTIONAL]], [[ independentGapConfig  ENUMERATED {supported}  OPTIONAL,periodicEUTRA-MeasAndReport ENUMERATED {supported} OPTIONAL,handoverFR1-FR2 ENUMERATED {supported} OPTIONAL,maxNumberCSI-RS-RRM-RS-SINR  ENUMERATED {n4, n8, n16, n32, n64, n96}OPTIONAL ]], }  or  MeasAndMobParametersCommon ::= SEQUENCE {  T312ENUMERATED {supported}  OPTIONAL,  T312-SCG ENUMERATED {supported} OPTIONAL, ...,  }

In another embodiment, In NR it is required to inform the network aboutthe UE support of T312 based early RLF declaration on NR when IRATEUTRAN based measurement report is triggered. Similarly, in LTE

In NR, indication of UE capability for IRAT T312 based early RLFdeclaration from NR to EUTRAN it is required to inform the network aboutthe UE support of T312 based early RLF declaration on LTE when IRAT NRbased measurement report is triggered. The same is illustrated below:

On NR (3GPP TS 38.331), T312 support for early RLF declaration whenEUTRAN measurement report is triggered.

MeasAndMobParametersCommon ::= SEQUENCE { supportedGapPattern BIT STRING(SIZE (22)) OPTIONAL, ssb-RLM  ENUMERATED {supported}  OPTIONAL,ssb-AndCSI-RS-RLM  ENUMERATED {supported} OPTIONAL, T312-EUTRA ENUMERATED {supported} OPTIONAL, ..., [[ eventB-MeasAndReport ENUMERATED {supported} OPTIONAL, handoverFDD-TDD  ENUMERATED{supported} OPTIONAL, eutra-CGI-Reporting ENUMERATED {supported}OPTIONAL, nr-CGI-Reporting ENUMERATED {supported} OPTIONAL ]], [[independentGapConfig  ENUMERATED {supported}  OPTIONAL,periodicEUTRA-MeasAndReport ENUMERATED {supported} OPTIONAL,handoverFR1-FR2 ENUMERATED {supported} OPTIONAL,maxNumberCSI-RS-RRM-RS-SINR ENUMERATED {n4, n8, n16, n32, n64, n96}OPTIONAL ]], }  or MeasAndMobParametersCommon ::=  SEQUENCE { T312-EUTRAENUMERATED {supported} OPTIONAL,  ..., }

On LTE (3GPP TS 36.331), T312 support for early RLF declaration whenEUTRAN measurement report is triggered.

4.3.6. x timerT312-r16: This field defines whether the UE supports T312based RLF when NR measurement report is triggered as specified in TS36.331 [5].

FIG. 6 is schematic view of the UE (100) for handling the RLF in thewireless communication system, according to embodiments as disclosedherein. The UE (100) can be, for example but not limited to a UnmannedAerial Vehicle (UAV), an airplane, a cellular phone, a tablet, a smartphone, a laptop, a Personal Digital Assistant (PDA), a globalpositioning system, a multimedia device, a video device, an internet ofthings (IoT) device, a smart watch, a game console, or the like. The UE(100) may also be referred to by those skilled in the art as a mobilestation, a subscriber station, a mobile unit, a subscriber unit, awireless unit, a remote unit, a mobile device, a wireless device, awireless communications device, a mobile subscriber station, an accessterminal, a mobile terminal, a wireless terminal, a remote terminal, ahandset, a user agent, a mobile client, or the like. The UE (100)includes a processor (110) having a SCG failure handling engine (110 a),a communicator (120), a memory (130), the first timer (140) and thesecond timer (150). The processor (110) is coupled with the communicator(120), the memory (130), the first timer (140) and the second timer(150).

The SCG failure handling engine (110 a) receives the measurementconfiguration including the second timer (150) from the SN (300).Further, the SCG failure handling engine (110 a) configures the UE (100)with the second timer (150) associated with the measurement report forthe PScell. Further, the SCG failure handling engine (110 a) starts thesecond timer (150) when the measurement report is triggered while thefirst timer (140) for the PSCell is running. Further, the SCG failurehandling engine (110 a) detect the expiry of one of: the first timer(140) and the second timer (150) for the PSCell. Further, the SCGfailure handling engine (110 a) declares the SCG RLF upon expiry of oneof the first timer (140) and the second timer (150) whichever is early.Further, the SCG failure handling engine (110 a) initiates a SCG failureprocedure towards a MN (200) upon declaring the SCG RLF.

In an embodiment, the processor (110) is configured to notify a SCGfailure message to the master node (200) over a SRB1 via a Master CellGroup (MCG) link upon declaring the SCG RLF. The SCG failure informationincludes a cause value corresponding to a failure type as one of: theexpiry of the first timer (140) and the expiry of the second timer(150).

In an embodiment, the processor (110) is configured to set the failuretype as one of the first timer expiry and the second timer expiry.

In an embodiment, the processor (110) sets the failure type as the firsttimer expiry, if the expiry of the first timer (140) is before theexpiry of the second timer (150), else the processor (110) sets thefailure type as the second timer expiry, if the expiry of the secondtimer (150) is before the expiry of the first timer (140).

In an embodiment, the processor (110) is configured to receive ameasurement object and reporting configuration including the secondtimer (150) from the SN (300). The second timer (150) is associated withthe measurement report for the PSCell of the SN (300).

In an embodiment, the SCG RLF is declared by stopping the first timer(140) based on the detection of the expiry of the second timer (150) forthe PSCell. In an embodiment, the SCG RLF is declared by stopping thesecond timer (150) based on the detection of the expiry of the firsttimer (150) for the PSCell.

In an embodiment, the first timer (140) is a T310 timer, wherein thefirst timer (140) is included during a SCG addition, and the secondtimer (150) is a T312 timer wherein the second timer (150) is includedin the measurement configuration from the SN (300)

In an embodiment, the measurement report is sent to the SN (300) overone of a SRB1 and the SRB3.

The processor (110) is configured to execute instructions stored in thememory (130) and to perform various processes. The communicator (120) isconfigured for communicating internally between internal hardwarecomponents and with external devices via one or more networks and/or MN(200) and the SN (300).

The memory (130) stores instructions to be executed by the processor(110). The memory (130) may include non-volatile storage elements.Examples of such non-volatile storage elements may include magnetic harddiscs, optical discs, floppy discs, flash memories, or forms ofelectrically programmable memories (EPROM) or electrically erasable andprogrammable (EEPROM) memories. In addition, the memory (130) may, insome examples, be considered a non-transitory storage medium. The term“non-transitory” may indicate that the storage medium is not embodied ina carrier wave or a propagated signal. However, the term“non-transitory” should not be interpreted that the memory (130) isnon-movable. In some examples, the memory (130) can be configured tostore larger amounts of information than the memory. In certainexamples, a non-transitory storage medium may store data that can, overtime, change (e.g., in Random Access Memory (RAM) or cache).

Although the FIG. 6 shows various hardware components of the UE (100)but it is to be understood that other embodiments are not limitedthereon. In other embodiments, the UE (100) may include less or morenumber of components. Further, the labels or names of the components areused only for illustrative purpose and does not limit the scope of theinvention. One or more components can be combined together to performsame or substantially similar function to handle the RLF in the wirelesscommunication system.

FIG. 7 is a flow chart (S700) illustrating a method for handling the RLFin the wireless communication system, according to embodiments asdisclosed herein. The operations (S702-S708) are performed by theprocessor (110).

At S702, the method includes receive a measurement configurationcomprising a second timer (150) from the SN (300). At S704, the methodincludes configure the UE (100) with the second timer (150) associatedwith the measurement report for the PScell. At S706, the method includesstarting the second timer (150) when the measurement report is triggeredwhile the first timer (140) for the PSCell is running. At S708, themethod includes detecting an expiry of one of: the first timer (140) andthe second timer (150) for the PSCell. At S710, the method includesdeclaring the SCG RLF upon expiry of one of the first timer (140) andthe second timer (150) whichever is early. At S712, the method includesinitiating the SCG failure procedure towards the MN (200) upon declaringthe SCG RLF.

The embodiments disclosed herein can be implemented using at least onesoftware program running on at least one hardware device and performingnetwork management functions to control the elements.

The various actions, acts, blocks, steps, or the like in the flow chart(S700) may be performed in the order presented, in a different order orsimultaneously. Further, in some embodiments, some of the actions, acts,blocks, steps, or the like may be omitted, added, modified, skipped, orthe like without departing from the scope of the invention.

FIG. 8 is a diagram illustrating a base station 800 according to anotherembodiment of the present disclosure.

Referring to the FIG. 8, the base station 800 may include a processor810, a transceiver 820 and a memory 830. However, all of the illustratedcomponents are not essential. The base station 800 may be implemented bymore or less components than those illustrated in FIG. 8. In addition,the processor 810 and the transceiver 820 and the memory 830 may beimplemented as a single chip according to another embodiment.

The aforementioned components will now be described in detail.

The processor 810 may include one or more processors or other processingdevices that control the proposed function, process, and/or method.Operation of the base station 800 may be implemented by the processor810.

The processor 810 may obtain at least one timer information includingtimer 312 for RLF on secondary cell group (SCG). The processor 810 maycontrol the transceiver to transmit control information including theobtained timer information. The processor 810 may, based on the timer312 being expired at a user equipment (UE), control the transceiver toreceive SCG failure information indicating the timer 312 expiry as acause of the RLF on the SCG.

The transceiver 820 may include a RF transmitter for up-converting andamplifying a transmitted signal, and a RF receiver for down-converting afrequency of a received signal. However, according to anotherembodiment, the transceiver 820 may be implemented by more or lesscomponents than those illustrated in components.

The transceiver 820 may be connected to the processor 810 and transmitand/or receive a signal. The signal may include control information anddata. In addition, the transceiver 820 may receive the signal through awireless channel and output the signal to the processor 810. Thetransceiver 820 may transmit a signal output from the processor 810through the wireless channel.

The memory 830 may store the control information or the data included ina signal obtained by the base station 800. The memory 830 may beconnected to the processor 810 and store at least one instruction or aprotocol or a parameter for the proposed function, process, and/ormethod. The memory 830 may include read-only memory (ROM) and/or randomaccess memory (RAM) and/or hard disk and/or CD-ROM and/or DVD and/orother storage devices.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the embodiments herein that others can, byapplying current knowledge, readily modify and/or adapt for variousapplications such specific embodiments without departing from thegeneric concept, and, therefore, such adaptations and modificationsshould and are intended to be comprehended within the meaning and rangeof equivalents of the disclosed embodiments. It is to be understood thatthe phraseology or terminology employed herein is for the purpose ofdescription and not of limitation. Therefore, while the embodimentsherein have been described in terms of preferred embodiments, thoseskilled in the art will recognize that the embodiments herein can bepracticed with modification within the spirit and scope of theembodiments as described herein.

1-37. (canceled)
 38. A method for handling a radio link failure (RLF) ina new radio (NR) wireless communication system comprising a master cellgroup (MCG) and a secondary cell group (SCG), the method performed by auser equipment (UE) comprising: receiving a measurement configurationcomprising information regarding a second timer from a secondary node(SN); in case that a measurement report type is set to event-triggeredand a measurement report event is triggered, identifying the secondtimer for a Primary SCG cell (PSCell); starting the second timer, incase that a first timer for the PSCell is running; detecting an expiryof one of: the first timer and the second timer for the PSCell;declaring a SCG RLF upon expiry of one of the first timer and the secondtimer; and initiating a SCG failure procedure upon declaring the SCGRLF.
 39. The method of claim 38, further comprising: based on theinitiation of the SCG failure procedure, transmitting a SCG failuremessage upon declaring the RLF of the SCG, wherein the SCG failuremessage includes a cause value corresponding to a failure type as theexpiry of the second timer.
 40. The method of claim 39, wherein the SCGfailure message is transmitted over a signaling radio bearer 1 (SRB1).41. The method of claim 38, further comprising: setting, by the UE, afailure type as one of a first timer expiry and a second timer expiry.42. The method of claim 38, wherein the SCG failure procedure isinitiated upon declaring the SCG RLF, in case that MCG transmission isnot suspended.
 43. The method of claim 38, further comprising:initiating, by the UE, a connection re-establishment procedure, in casethat the RLF is considered and MCG transmission is suspended.
 44. Themethod of claim 38, wherein the SCG RLF is declared by stopping thefirst timer based on the detection of the expiry of the second timer.45. The method of claim 38, wherein the first timer is a T310 timer, andthe second timer is a T312 timer.
 46. The method of claim 45, the T312timer is configured based on the measurement configuration.
 47. A UserEquipment (UE) configured to handle a radio link failure (RLF) in a newradio (NR) wireless communication system comprising a master cell group(MCG) and a secondary cell group (SCG), the UE comprising: atransceiver; a memory; and a processor, coupled with the memory,configured to: receive, via the transceiver, a measurement configurationcomprising information regarding a second timer from a secondary node(SN); in case that a measurement report type is set to event-triggeredand a measurement report event is triggered, identify the second timerfor a Primary secondary cell (PSCell); start the second timer in casethat a first timer for the PSCell is running; detect an expiry of oneof: the first timer and the second timer for the PSCell; declare a SCGRLF upon expiry of one of the first timer and the second timer; andinitiate a SCG failure procedure upon declaring the SCG RLF.
 48. The UEof claim 47, wherein the processor is configured to based on theinitiation of the SCG failure procedure, transmit, via the transceiver,a SCG failure message, upon declaring the RLF of the SCG, wherein theSCG failure message includes a cause value corresponding to a failuretype as the expiry of the second timer.
 49. The UE of claim 48, whereinthe SCG failure message is transmitted over a signaling radio bearer 1(SRB1).
 50. The UE of claim 47, wherein the processor is configured toset a failure type as one of a first timer expiry and a second timerexpiry.
 51. The UE of claim 47, wherein the processor is configured toinitiate a connection re-establishment procedure, in case that the RLFis considered and MCG transmission is suspended.
 52. The UE of claim 47,wherein the first timer is a T310 timer, and the second timer is a T312timer.
 53. The UE of claim 52, wherein the T312 timer is configuredbased on the measurement configuration.
 54. The UE of claim 47, whereinthe SCG failure procedure is initiated upon declaring the SCG RLF, incase that MCG transmission is not suspended.